diff --git a/app/models/global_milestone.rb b/app/models/global_milestone.rb
index af4780f78d0..18af3c41d61 100644
--- a/app/models/global_milestone.rb
+++ b/app/models/global_milestone.rb
@@ -158,6 +158,6 @@ class GlobalMilestone
   end
 
   def human_total_time_spent
-    Gitlab::TimeTrackingFormatter.output(total_time_spent) || 0
+    Gitlab::TimeTrackingFormatter.output(total_time_spent)
   end
 end
diff --git a/app/models/milestone.rb b/app/models/milestone.rb
index 5e174a15c91..fa2dfcb694b 100644
--- a/app/models/milestone.rb
+++ b/app/models/milestone.rb
@@ -218,7 +218,7 @@ class Milestone < ActiveRecord::Base
   end
 
   def human_total_time_spent
-    Gitlab::TimeTrackingFormatter.output(total_time_spent) || 0
+    Gitlab::TimeTrackingFormatter.output(total_time_spent)
   end
 
   private
diff --git a/app/views/shared/icons/_icon_hourglass.svg b/app/views/shared/icons/_icon_hourglass.svg
new file mode 100644
index 00000000000..fe7e497ce13
--- /dev/null
+++ b/app/views/shared/icons/_icon_hourglass.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 16 16"><path d="M10.331 4.889A2.988 2.988 0 0 0 11 3V2H5v1c0 .362.064.709.182 1.03l5.15.859zM3 14v-1c0-1.78.93-3.342 2.33-4.228.447-.327.67-.582.67-.764 0-.19-.242-.46-.725-.815A4.996 4.996 0 0 1 3 3V2H2a1 1 0 1 1 0-2h12a1 1 0 0 1 0 2h-1v1a4.997 4.997 0 0 1-2.39 4.266c-.407.3-.61.545-.61.734 0 .19.203.434.61.734A4.997 4.997 0 0 1 13 13v1h1a1 1 0 0 1 0 2H2a1 1 0 0 1 0-2h1zm8 0v-1a3 3 0 0 0-6 0v1h6z"/></svg>
diff --git a/app/views/shared/milestones/_sidebar.html.haml b/app/views/shared/milestones/_sidebar.html.haml
index 6267151f460..65e70f13055 100644
--- a/app/views/shared/milestones/_sidebar.html.haml
+++ b/app/views/shared/milestones/_sidebar.html.haml
@@ -87,13 +87,19 @@
 
     .block.time_spent
       .sidebar-collapsed-icon
-        %strong
-          = custom_icon('icon_clock_o')
-        %span= milestone.human_total_time_spent
+        = custom_icon('icon_hourglass')
+        %span.collapsed-milestone-total-time-spent
+        - if milestone.human_total_time_spent
+          = milestone.human_total_time_spent
+        - else
+          None
       .title.hide-collapsed
         Total time spent
       .value.hide-collapsed
-        = milestone.human_total_time_spent
+        - if milestone.human_total_time_spent
+          %span.bold= milestone.human_total_time_spent
+        -else
+          %span.no-value No time spent
 
     .block.merge-requests
       .sidebar-collapsed-icon
diff --git a/changelogs/unreleased/39335-add-time-spend-to-milestones.yml b/changelogs/unreleased/39335-add-time-spend-to-milestones.yml
new file mode 100644
index 00000000000..41a43418cbf
--- /dev/null
+++ b/changelogs/unreleased/39335-add-time-spend-to-milestones.yml
@@ -0,0 +1,5 @@
+---
+title: Add total time spent to milestones
+merge_request: 15116
+author: George Andrinopoulos
+type: added