diff --git a/Dangerfile b/Dangerfile
index 469e77b2514..6a2c5cf2773 100644
--- a/Dangerfile
+++ b/Dangerfile
@@ -8,5 +8,6 @@ danger.import_dangerfile(path: 'danger/database')
 danger.import_dangerfile(path: 'danger/documentation')
 danger.import_dangerfile(path: 'danger/frozen_string')
 danger.import_dangerfile(path: 'danger/commit_messages')
+danger.import_dangerfile(path: 'danger/duplicate_yarn_dependencies')
 danger.import_dangerfile(path: 'danger/prettier')
 danger.import_dangerfile(path: 'danger/eslint')
diff --git a/danger/duplicate_yarn_dependencies/Dangerfile b/danger/duplicate_yarn_dependencies/Dangerfile
new file mode 100644
index 00000000000..25f81ec86a4
--- /dev/null
+++ b/danger/duplicate_yarn_dependencies/Dangerfile
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+return unless helper.all_changed_files.include? 'yarn.lock'
+
+duplicate = `node_modules/.bin/yarn-deduplicate --list --strategy fewer yarn.lock`
+             .split(/$/)
+             .map(&:strip)
+             .reject(&:empty?)
+
+return if duplicate.empty?
+
+warn 'This merge request has introduced duplicated yarn dependencies.'
+
+markdown(<<~MARKDOWN)
+  ## Duplicate yarn dependencies
+
+  The following dependencies should be de-duplicated:
+
+  * #{duplicate.map { |path| "`#{path}`" }.join("\n* ")}
+
+  Please run the following command and commit the changes to `yarn.lock`:
+
+  ```
+  node_modules/.bin/yarn-deduplicate --strategy fewer yarn.lock \\
+    && yarn install
+  ```
+MARKDOWN
diff --git a/package.json b/package.json
index cf7e43f14dd..44423c97722 100644
--- a/package.json
+++ b/package.json
@@ -158,7 +158,8 @@
     "nodemon": "^1.18.4",
     "prettier": "1.15.2",
     "vue-jest": "^3.0.1",
-    "webpack-dev-server": "^3.1.10"
+    "webpack-dev-server": "^3.1.10",
+    "yarn-deduplicate": "^1.0.5"
   },
   "engines": {
     "yarn": "^1.10.0"
diff --git a/yarn.lock b/yarn.lock
index a6b43f785dc..999293bce56 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -900,6 +900,11 @@
   resolved "https://registry.yarnpkg.com/@xtuc/long/-/long-4.2.1.tgz#5c85d662f76fa1d34575766c5dcd6615abcd30d8"
   integrity sha512-FZdkNBDqBRHKQ2MEbSC17xnPFOhZxeJ2YGSfr2BKf3sujG49Qe3bB+rGCwQfIaA7WHnGeGkSijX4FuBCdrzW/g==
 
+"@yarnpkg/lockfile@^1.1.0":
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/@yarnpkg/lockfile/-/lockfile-1.1.0.tgz#e77a97fbd345b76d83245edcd17d393b1b41fb31"
+  integrity sha512-GpSwvyXOcOOlV70vbnzjj4fW5xW/FdUF6nQEt1ENy7m4ZCczi1+/buVUPAqmGfqznsORNFzUMjctTIp8a9tuCQ==
+
 abab@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/abab/-/abab-2.0.0.tgz#aba0ab4c5eee2d4c79d3487d85450fb2376ebb0f"
@@ -2301,7 +2306,7 @@ combined-stream@^1.0.6, combined-stream@~1.0.6:
   dependencies:
     delayed-stream "~1.0.0"
 
-commander@2, commander@^2.18.0, commander@^2.19.0:
+commander@2, commander@^2.10.0, commander@^2.18.0, commander@^2.19.0:
   version "2.19.0"
   resolved "https://registry.yarnpkg.com/commander/-/commander-2.19.0.tgz#f6198aa84e5b83c46054b94ddedbfed5ee9ff12a"
   integrity sha512-6tvAOO+D6OENvRAh524Dh9jcfKTYDQAqvqezbCW82xj5X0pSrcpxtvRKHLG0yBY6SD7PSDrJaj+0AiOcKVd1Xg==
@@ -10450,6 +10455,15 @@ yargs@^11.0.0:
     y18n "^3.2.1"
     yargs-parser "^9.0.2"
 
+yarn-deduplicate@^1.0.5:
+  version "1.0.5"
+  resolved "https://registry.yarnpkg.com/yarn-deduplicate/-/yarn-deduplicate-1.0.5.tgz#e56016f1c29e77e323f401ea838f5e8c7cdbfd42"
+  integrity sha512-4nds6N7dxuXcfUZAVaSUVSlI4TvwEdMaZg/DRBf/KM3iFezNBdkhcTYptcwKaecAYAfVxx3g0Ex21kssSr8YsA==
+  dependencies:
+    "@yarnpkg/lockfile" "^1.1.0"
+    commander "^2.10.0"
+    semver "^5.3.0"
+
 yeast@0.1.2:
   version "0.1.2"
   resolved "https://registry.yarnpkg.com/yeast/-/yeast-0.1.2.tgz#008e06d8094320c372dbc2f8ed76a0ca6c8ac419"