diff --git a/app/assets/javascripts/dropzone_input.js b/app/assets/javascripts/dropzone_input.js
index b3a76fbb43e..988c484ed85 100644
--- a/app/assets/javascripts/dropzone_input.js
+++ b/app/assets/javascripts/dropzone_input.js
@@ -5,104 +5,154 @@ require('./preview_markdown');
 
 window.DropzoneInput = (function() {
   function DropzoneInput(form) {
-    var $mdArea, alertAttr, alertClass, appendToTextArea, btnAlert, child, closeAlertMessage, closeSpinner, divAlert, divHover, divSpinner, dropzone, form_dropzone, form_textarea, getFilename, handlePaste, iconPaperclip, iconSpinner, insertToTextArea, isImage, max_file_size, pasteText, uploads_path, showError, showSpinner, uploadFile, uploadProgress;
+    var updateAttachingMessage, $attachingFileMessage, $mdArea, $attachButton, $cancelButton, $retryLink, $uploadingErrorContainer, $uploadingErrorMessage, $uploadProgress, $uploadingProgressContainer, appendToTextArea, btnAlert, child, closeAlertMessage, closeSpinner, divHover, divSpinner, dropzone, $formDropzone, formTextarea, getFilename, handlePaste, iconPaperclip, iconSpinner, insertToTextArea, isImage, maxFileSize, pasteText, uploadsPath, showError, showSpinner, uploadFile;
     Dropzone.autoDiscover = false;
-    alertClass = "alert alert-danger alert-dismissable div-dropzone-alert";
-    alertAttr = "class=\"close\" data-dismiss=\"alert\"" + "aria-hidden=\"true\"";
-    divHover = "<div class=\"div-dropzone-hover\"></div>";
-    divSpinner = "<div class=\"div-dropzone-spinner\"></div>";
-    divAlert = "<div class=\"" + alertClass + "\"></div>";
-    iconPaperclip = "<i class=\"fa fa-paperclip div-dropzone-icon\"></i>";
-    iconSpinner = "<i class=\"fa fa-spinner fa-spin div-dropzone-icon\"></i>";
-    uploadProgress = $("<div class=\"div-dropzone-progress\"></div>");
-    btnAlert = "<button type=\"button\"" + alertAttr + ">&times;</button>";
-    uploads_path = window.uploads_path || null;
-    max_file_size = gon.max_file_size || 10;
-    form_textarea = $(form).find(".js-gfm-input");
-    form_textarea.wrap("<div class=\"div-dropzone\"></div>");
-    form_textarea.on('paste', (function(_this) {
+    divHover = '<div class="div-dropzone-hover"></div>';
+    iconPaperclip = '<i class="fa fa-paperclip div-dropzone-icon"></i>';
+    $attachButton = form.find('.button-attach-file');
+    $attachingFileMessage = form.find('.attaching-file-message');
+    $cancelButton = form.find('.button-cancel-uploading-files');
+    $retryLink = form.find('.retry-uploading-link');
+    $uploadProgress = form.find('.uploading-progress');
+    $uploadingErrorContainer = form.find('.uploading-error-container');
+    $uploadingErrorMessage = form.find('.uploading-error-message');
+    $uploadingProgressContainer = form.find('.uploading-progress-container');
+    uploadsPath = window.uploads_path || null;
+    maxFileSize = gon.max_file_size || 10;
+    formTextarea = form.find('.js-gfm-input');
+    formTextarea.wrap('<div class="div-dropzone"></div>');
+    formTextarea.on('paste', (function(_this) {
       return function(event) {
         return handlePaste(event);
       };
     })(this));
-    $mdArea = $(form_textarea).closest('.md-area');
-    $(form).setupMarkdownPreview();
-    form_dropzone = $(form).find('.div-dropzone');
-    form_dropzone.parent().addClass("div-dropzone-wrapper");
-    form_dropzone.append(divHover);
-    form_dropzone.find(".div-dropzone-hover").append(iconPaperclip);
-    form_dropzone.append(divSpinner);
-    form_dropzone.find(".div-dropzone-spinner").append(iconSpinner);
-    form_dropzone.find(".div-dropzone-spinner").append(uploadProgress);
-    form_dropzone.find(".div-dropzone-spinner").css({
-      "opacity": 0,
-      "display": "none"
-    });
 
-    if (!uploads_path) return;
+    // Add dropzone area to the form.
+    $mdArea = formTextarea.closest('.md-area');
+    form.setupMarkdownPreview();
+    $formDropzone = form.find('.div-dropzone');
+    $formDropzone.parent().addClass('div-dropzone-wrapper');
+    $formDropzone.append(divHover);
+    $formDropzone.find('.div-dropzone-hover').append(iconPaperclip);
 
-    dropzone = form_dropzone.dropzone({
-      url: uploads_path,
-      dictDefaultMessage: "",
+    if (!uploadsPath) return;
+
+    dropzone = $formDropzone.dropzone({
+      url: uploadsPath,
+      dictDefaultMessage: '',
       clickable: true,
-      paramName: "file",
-      maxFilesize: max_file_size,
+      paramName: 'file',
+      maxFilesize: maxFileSize,
       uploadMultiple: false,
       headers: {
-        "X-CSRF-Token": $("meta[name=\"csrf-token\"]").attr("content")
+        'X-CSRF-Token': $('meta[name="csrf-token"]').attr('content')
       },
       previewContainer: false,
       processing: function() {
-        return $(".div-dropzone-alert").alert("close");
+        return $('.div-dropzone-alert').alert('close');
       },
       dragover: function() {
         $mdArea.addClass('is-dropzone-hover');
-        form.find(".div-dropzone-hover").css("opacity", 0.7);
+        form.find('.div-dropzone-hover').css('opacity', 0.7);
       },
       dragleave: function() {
         $mdArea.removeClass('is-dropzone-hover');
-        form.find(".div-dropzone-hover").css("opacity", 0);
+        form.find('.div-dropzone-hover').css('opacity', 0);
       },
       drop: function() {
         $mdArea.removeClass('is-dropzone-hover');
-        form.find(".div-dropzone-hover").css("opacity", 0);
-        form_textarea.focus();
+        form.find('.div-dropzone-hover').css('opacity', 0);
+        formTextarea.focus();
       },
       success: function(header, response) {
         const processingFileCount = this.getQueuedFiles().length + this.getUploadingFiles().length;
         const shouldPad = processingFileCount >= 1;
 
         pasteText(response.link.markdown, shouldPad);
+        // Show 'Attach a file' link only when all files have been uploaded.
+        if (!processingFileCount) $attachButton.removeClass('hide');
       },
-      error: function(temp) {
-        var checkIfMsgExists, errorAlert;
-        errorAlert = $(form).find('.error-alert');
-        checkIfMsgExists = errorAlert.children().length;
-        if (checkIfMsgExists === 0) {
-          errorAlert.append(divAlert);
-          $(".div-dropzone-alert").append(btnAlert + "Attaching the file failed.");
-        }
+      error: function(file, errorMessage = 'Attaching the file failed.', xhr) {
+        // If 'error' event is fired by dropzone, the second parameter is error message.
+        // If the 'errorMessage' parameter is empty, the default error message is set.
+        // If the 'error' event is fired by backend (xhr) error response, the third parameter is
+        // xhr object (xhr.responseText is error message).
+        // On error we hide the 'Attach' and 'Cancel' buttons
+        // and show an error.
+
+        // If there's xhr error message, let's show it instead of dropzone's one.
+        const message = xhr ? xhr.responseText : errorMessage;
+
+        $uploadingErrorContainer.removeClass('hide');
+        $uploadingErrorMessage.html(message);
+        $attachButton.addClass('hide');
+        $cancelButton.addClass('hide');
       },
       totaluploadprogress: function(totalUploadProgress) {
-        uploadProgress.text(Math.round(totalUploadProgress) + "%");
+        updateAttachingMessage(this.files, $attachingFileMessage);
+        $uploadProgress.text(Math.round(totalUploadProgress) + '%');
       },
-      sending: function() {
-        form_dropzone.find(".div-dropzone-spinner").css({
-          "opacity": 0.7,
-          "display": "inherit"
-        });
+      sending: function(file) {
+        // DOM elements already exist.
+        // Instead of dynamically generating them,
+        // we just either hide or show them.
+        $attachButton.addClass('hide');
+        $uploadingErrorContainer.addClass('hide');
+        $uploadingProgressContainer.removeClass('hide');
+        $cancelButton.removeClass('hide');
+      },
+      removedfile: function() {
+        $attachButton.removeClass('hide');
+        $cancelButton.addClass('hide');
+        $uploadingProgressContainer.addClass('hide');
+        $uploadingErrorContainer.addClass('hide');
       },
       queuecomplete: function() {
-        uploadProgress.text("");
-        $(".dz-preview").remove();
-        $(".markdown-area").trigger("input");
-        $(".div-dropzone-spinner").css({
-          "opacity": 0,
-          "display": "none"
-        });
+        $('.dz-preview').remove();
+        $('.markdown-area').trigger('input');
+
+        $uploadingProgressContainer.addClass('hide');
+        $cancelButton.addClass('hide');
       }
     });
-    child = $(dropzone[0]).children("textarea");
+
+    child = $(dropzone[0]).children('textarea');
+
+    // removeAllFiles(true) stops uploading files (if any)
+    // and remove them from dropzone files queue.
+    $cancelButton.on('click', (e) => {
+      const target = e.target.closest('form').querySelector('.div-dropzone');
+
+      e.preventDefault();
+      e.stopPropagation();
+      Dropzone.forElement(target).removeAllFiles(true);
+    });
+
+    // If 'error' event is fired, we store a failed files,
+    // clear dropzone files queue, change status of failed files to undefined,
+    // and add that files to the dropzone files queue again.
+    // addFile() adds file to dropzone files queue and upload it.
+    $retryLink.on('click', (e) => {
+      const dropzoneInstance = Dropzone.forElement(e.target.closest('form').querySelector('.div-dropzone'));
+      const failedFiles = dropzoneInstance.files;
+
+      e.preventDefault();
+
+      // 'true' parameter of removeAllFiles() cancels uploading of files that are being uploaded at the moment.
+      dropzoneInstance.removeAllFiles(true);
+
+      failedFiles.map((failedFile, i) => {
+        const file = failedFile;
+
+        if (file.status === Dropzone.ERROR) {
+          file.status = undefined;
+          file.accepted = undefined;
+        }
+
+        return dropzoneInstance.addFile(file);
+      });
+    });
+
     handlePaste = function(event) {
       var filename, image, pasteEvent, text;
       pasteEvent = event.originalEvent;
@@ -110,25 +160,27 @@ window.DropzoneInput = (function() {
         image = isImage(pasteEvent);
         if (image) {
           event.preventDefault();
-          filename = getFilename(pasteEvent) || "image.png";
-          text = "{{" + filename + "}}";
+          filename = getFilename(pasteEvent) || 'image.png';
+          text = `{{${filename}}}`;
           pasteText(text);
           return uploadFile(image.getAsFile(), filename);
         }
       }
     };
+
     isImage = function(data) {
       var i, item;
       i = 0;
       while (i < data.clipboardData.items.length) {
         item = data.clipboardData.items[i];
-        if (item.type.indexOf("image") !== -1) {
+        if (item.type.indexOf('image') !== -1) {
           return item;
         }
         i += 1;
       }
       return false;
     };
+
     pasteText = function(text, shouldPad) {
       var afterSelection, beforeSelection, caretEnd, caretStart, textEnd;
       var formattedText = text;
@@ -142,31 +194,33 @@ window.DropzoneInput = (function() {
       $(child).val(beforeSelection + formattedText + afterSelection);
       textarea.setSelectionRange(caretStart + formattedText.length, caretEnd + formattedText.length);
       textarea.style.height = `${textarea.scrollHeight}px`;
-      return form_textarea.trigger("input");
+      return formTextarea.trigger('input');
     };
+
     getFilename = function(e) {
       var value;
       if (window.clipboardData && window.clipboardData.getData) {
-        value = window.clipboardData.getData("Text");
+        value = window.clipboardData.getData('Text');
       } else if (e.clipboardData && e.clipboardData.getData) {
-        value = e.clipboardData.getData("text/plain");
+        value = e.clipboardData.getData('text/plain');
       }
       value = value.split("\r");
       return value.first();
     };
+
     uploadFile = function(item, filename) {
       var formData;
       formData = new FormData();
-      formData.append("file", item, filename);
+      formData.append('file', item, filename);
       return $.ajax({
-        url: uploads_path,
-        type: "POST",
+        url: uploadsPath,
+        type: 'POST',
         data: formData,
-        dataType: "json",
+        dataType: 'json',
         processData: false,
         contentType: false,
         headers: {
-          "X-CSRF-Token": $("meta[name=\"csrf-token\"]").attr("content")
+          'X-CSRF-Token': $('meta[name="csrf-token"]').attr('content')
         },
         beforeSend: function() {
           showSpinner();
@@ -183,44 +237,54 @@ window.DropzoneInput = (function() {
         }
       });
     };
+
+    updateAttachingMessage = (files, messageContainer) => {
+      let attachingMessage;
+      const filesCount = files.filter(function(file) {
+        return file.status === 'uploading' ||
+               file.status === 'queued';
+      }).length;
+
+      // Dinamycally change uploading files text depending on files number in
+      // dropzone files queue.
+      if (filesCount > 1) {
+        attachingMessage = 'Attaching ' + filesCount + ' files -';
+      } else {
+        attachingMessage = 'Attaching a file -';
+      }
+
+      messageContainer.text(attachingMessage);
+    };
+
     insertToTextArea = function(filename, url) {
       return $(child).val(function(index, val) {
-        return val.replace("{{" + filename + "}}", url);
+        return val.replace(`{{${filename}}}`, url);
       });
     };
+
     appendToTextArea = function(url) {
       return $(child).val(function(index, val) {
         return val + url + "\n";
       });
     };
+
     showSpinner = function(e) {
-      return form.find(".div-dropzone-spinner").css({
-        "opacity": 0.7,
-        "display": "inherit"
-      });
+      return $uploadingProgressContainer.removeClass('hide');
     };
+
     closeSpinner = function() {
-      return form.find(".div-dropzone-spinner").css({
-        "opacity": 0,
-        "display": "none"
-      });
+      return $uploadingProgressContainer.addClass('hide');
     };
+
     showError = function(message) {
-      var checkIfMsgExists, errorAlert;
-      errorAlert = $(form).find('.error-alert');
-      checkIfMsgExists = errorAlert.children().length;
-      if (checkIfMsgExists === 0) {
-        errorAlert.append(divAlert);
-        return $(".div-dropzone-alert").append(btnAlert + message);
-      }
+      $uploadingErrorContainer.removeClass('hide');
+      $uploadingErrorMessage.html(message);
     };
-    closeAlertMessage = function() {
-      return form.find(".div-dropzone-alert").alert("close");
-    };
-    form.find(".markdown-selector").click(function(e) {
+
+    form.find('.markdown-selector').click(function(e) {
       e.preventDefault();
       $(this).closest('.gfm-form').find('.div-dropzone').click();
-      form_textarea.focus();
+      formTextarea.focus();
     });
   }
 
diff --git a/app/assets/stylesheets/pages/note_form.scss b/app/assets/stylesheets/pages/note_form.scss
index 62f654ed343..9db26f99a75 100644
--- a/app/assets/stylesheets/pages/note_form.scss
+++ b/app/assets/stylesheets/pages/note_form.scss
@@ -277,6 +277,7 @@
 .toolbar-text {
   font-size: 14px;
   line-height: 16px;
+  margin-top: 2px;
 
   @media (min-width: $screen-md-min) {
     float: left;
@@ -402,3 +403,45 @@
     }
   }
 }
+
+.uploading-container {
+  float: right;
+
+  @media (max-width: $screen-xs-max) {
+    float: left;
+    margin-top: 5px;
+  }
+}
+
+.uploading-error-icon,
+.uploading-error-message {
+  color: $gl-text-red;
+}
+
+.uploading-error-message {
+  @media (max-width: $screen-xs-max) {
+    &::after {
+      content: "\a";
+      white-space: pre;
+    }
+  }
+}
+
+.uploading-progress {
+  margin-right: 5px;
+}
+
+.attach-new-file,
+.button-attach-file,
+.retry-uploading-link {
+  color: $gl-link-color;
+  padding: 0;
+  background: none;
+  border: 0;
+  font-size: 14px;
+  line-height: 16px;
+}
+
+.markdown-selector {
+  color: $gl-link-color;
+}
diff --git a/app/helpers/icons_helper.rb b/app/helpers/icons_helper.rb
index 55fa81e95ef..0c6ce04a4c9 100644
--- a/app/helpers/icons_helper.rb
+++ b/app/helpers/icons_helper.rb
@@ -7,9 +7,10 @@ module IconsHelper
   # font-awesome-rails gem, but should we ever use a different icon pack in the
   # future we won't have to change hundreds of method calls.
   def icon(names, options = {})
-    if (options.keys & %w[aria-hidden aria-label]).empty?
-      # Add `aria-hidden` if there are no aria's set
+    if (options.keys & %w[aria-hidden aria-label data-hidden]).empty?
+      # Add 'aria-hidden' and 'data-hidden' if they are not set in options.
       options['aria-hidden'] = true
+      options['data-hidden'] = true
     end
 
     options.include?(:base) ? fa_stacked_icon(names, options) : fa_icon(names, options)
diff --git a/app/views/shared/notes/_hints.html.haml b/app/views/shared/notes/_hints.html.haml
index 81d97eabe65..7ce6130de60 100644
--- a/app/views/shared/notes/_hints.html.haml
+++ b/app/views/shared/notes/_hints.html.haml
@@ -9,6 +9,27 @@
     - else
       is
     supported
-  %button.toolbar-button.markdown-selector{ type: 'button', tabindex: '-1' }
-    = icon('file-image-o', class: 'toolbar-button-icon')
-    Attach a file
+
+  %span.uploading-container
+    %span.uploading-progress-container.hide
+      = icon('file-image-o', class: 'toolbar-button-icon')
+      %span.attaching-file-message
+        -# Populated by app/assets/javascripts/dropzone_input.js
+      %span.uploading-progress 0%
+      %span.uploading-spinner
+        = icon('spinner spin', class: 'toolbar-button-icon')
+
+    %span.uploading-error-container.hide
+      %span.uploading-error-icon
+        = icon('file-image-o', class: 'toolbar-button-icon')
+      %span.uploading-error-message
+        -# Populated by app/assets/javascripts/dropzone_input.js
+      %button.retry-uploading-link{ type: 'button' } Try again
+      or
+      %button.attach-new-file.markdown-selector{ type: 'button' } attach a new file
+
+    %button.markdown-selector.button-attach-file{ type: 'button', tabindex: '-1' }
+      = icon('file-image-o', class: 'toolbar-button-icon')
+      Attach a file
+
+    %button.btn.btn-default.btn-xs.hide.button-cancel-uploading-files{ type: 'button' } Cancel
diff --git a/changelogs/unreleased/add_ability_to_cancel_attaching_file_and_redesign_attaching_files_ui.yml b/changelogs/unreleased/add_ability_to_cancel_attaching_file_and_redesign_attaching_files_ui.yml
new file mode 100644
index 00000000000..fcf4efa2846
--- /dev/null
+++ b/changelogs/unreleased/add_ability_to_cancel_attaching_file_and_redesign_attaching_files_ui.yml
@@ -0,0 +1,4 @@
+---
+title: Add an ability to cancel attaching file and redesign attaching files UI
+merge_request: 9431
+author: blackst0ne
diff --git a/spec/features/uploads/user_uploads_file_to_note_spec.rb b/spec/features/uploads/user_uploads_file_to_note_spec.rb
index 0c160dd74b4..8f03024ea06 100644
--- a/spec/features/uploads/user_uploads_file_to_note_spec.rb
+++ b/spec/features/uploads/user_uploads_file_to_note_spec.rb
@@ -5,18 +5,78 @@ feature 'User uploads file to note', feature: true do
 
   let(:user) { create(:user) }
   let(:project) { create(:empty_project, creator: user, namespace: user.namespace) }
+  let(:issue) { create(:issue, project: project, author: user) }
 
-  scenario 'they see the attached file', js: true do
-    issue = create(:issue, project: project, author: user)
-
+  before do
     login_as(user)
     visit namespace_project_issue_path(project.namespace, project, issue)
+  end
 
-    dropzone_file(Rails.root.join('spec', 'fixtures', 'dk.png'))
-    click_button 'Comment'
-    wait_for_ajax
+  context 'before uploading' do
+    it 'shows "Attach a file" button', js: true do
+      expect(page).to have_button('Attach a file')
+      expect(page).not_to have_selector('.uploading-progress-container', visible: true)
+    end
+  end
 
-    expect(find('a.no-attachment-icon img[alt="dk"]')['src'])
-      .to match(%r{/#{project.full_path}/uploads/\h{32}/dk\.png$})
+  context 'uploading is in progress' do
+    it 'shows "Cancel" button on uploading', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'dk.png')], 0, false)
+
+      expect(page).to have_button('Cancel')
+    end
+
+    it 'cancels uploading on clicking to "Cancel" button', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'dk.png')], 0, false)
+
+      click_button 'Cancel'
+
+      expect(page).to have_button('Attach a file')
+      expect(page).not_to have_button('Cancel')
+      expect(page).not_to have_selector('.uploading-progress-container', visible: true)
+    end
+
+    it 'shows "Attaching a file" message on uploading 1 file', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'dk.png')], 0, false)
+
+      expect(page).to have_selector('.attaching-file-message', visible: true, text: 'Attaching a file -')
+    end
+
+    it 'shows "Attaching 2 files" message on uploading 2 file', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'video_sample.mp4'),
+                     Rails.root.join('spec', 'fixtures', 'dk.png')], 0, false)
+
+      expect(page).to have_selector('.attaching-file-message', visible: true, text: 'Attaching 2 files -')
+    end
+
+    it 'shows error message, "retry" and "attach a new file" link a if file is too big', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'video_sample.mp4')], 0.01)
+
+      error_text = 'File is too big (0.06MiB). Max filesize: 0.01MiB.'
+
+      expect(page).to have_selector('.uploading-error-message', visible: true, text: error_text)
+      expect(page).to have_selector('.retry-uploading-link', visible: true, text: 'Try again')
+      expect(page).to have_selector('.attach-new-file', visible: true, text: 'attach a new file')
+      expect(page).not_to have_button('Attach a file')
+    end
+  end
+
+  context 'uploading is complete' do
+    it 'shows "Attach a file" button on uploading complete', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'dk.png')])
+      wait_for_ajax
+
+      expect(page).to have_button('Attach a file')
+      expect(page).not_to have_selector('.uploading-progress-container', visible: true)
+    end
+
+    scenario 'they see the attached file', js: true do
+      dropzone_file([Rails.root.join('spec', 'fixtures', 'dk.png')])
+      click_button 'Comment'
+      wait_for_ajax
+
+      expect(find('a.no-attachment-icon img[alt="dk"]')['src'])
+        .to match(%r{/#{project.full_path}/uploads/\h{32}/dk\.png$})
+    end
   end
 end
diff --git a/spec/support/dropzone_helper.rb b/spec/support/dropzone_helper.rb
index 984ec7d2741..02fdeb08afe 100644
--- a/spec/support/dropzone_helper.rb
+++ b/spec/support/dropzone_helper.rb
@@ -6,32 +6,52 @@ module DropzoneHelper
   # Dropzone events to perform the actual upload.
   #
   # This method waits for the upload to complete before returning.
-  def dropzone_file(file_path)
+  # max_file_size is an optional parameter.
+  # If it's not 0, then it used in dropzone.maxFilesize parameter.
+  # wait_for_queuecomplete is an optional parameter.
+  # If it's 'false', then the helper will NOT wait for backend response
+  # It lets to test behaviors while AJAX is processing.
+  def dropzone_file(files, max_file_size = 0, wait_for_queuecomplete = true)
     # Generate a fake file input that Capybara can attach to
     page.execute_script <<-JS.strip_heredoc
+      $('#fakeFileInput').remove();
       var fakeFileInput = window.$('<input/>').attr(
-        {id: 'fakeFileInput', type: 'file'}
+        {id: 'fakeFileInput', type: 'file', multiple: true}
       ).appendTo('body');
 
       window._dropzoneComplete = false;
     JS
 
-    # Attach the file to the fake input selector with Capybara
-    attach_file('fakeFileInput', file_path)
+    # Attach files to the fake input selector with Capybara
+    attach_file('fakeFileInput', files)
 
     # Manually trigger a Dropzone "drop" event with the fake input's file list
     page.execute_script <<-JS.strip_heredoc
-      var fileList = [$('#fakeFileInput')[0].files[0]];
-      var e = jQuery.Event('drop', { dataTransfer : { files : fileList } });
-
       var dropzone = $('.div-dropzone')[0].dropzone;
+      dropzone.options.autoProcessQueue = false;
+
+      if (#{max_file_size} > 0) {
+        dropzone.options.maxFilesize = #{max_file_size};
+      }
+
       dropzone.on('queuecomplete', function() {
         window._dropzoneComplete = true;
       });
-      dropzone.listeners[0].events.drop(e);
+
+      var fileList = [$('#fakeFileInput')[0].files];
+
+      $.map(fileList, function(file){
+        var e = jQuery.Event('drop', { dataTransfer : { files : file } });
+
+        dropzone.listeners[0].events.drop(e);
+      });
+
+      dropzone.processQueue();
     JS
 
-    # Wait until Dropzone's fired `queuecomplete`
-    loop until page.evaluate_script('window._dropzoneComplete === true')
+    if wait_for_queuecomplete
+      # Wait until Dropzone's fired `queuecomplete`
+      loop until page.evaluate_script('window._dropzoneComplete === true')
+    end
   end
 end