diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 1853c6048be9eca6d9cc36b8319fb53e05faba07..061f296dc511538a8a910c224edeea2a855ce938 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Remove deprecated `Hash#diff` with no replacement.
+
+    If you're using it to compare hashes for the purpose of testing, please use
+    MiniTest's `assert_equal` instead.
+
+    *Carlos Antonio da Silva*
+
 *   Remove deprecated `Date#to_time_in_current_zone` in favour of `Date#in_time_zone`.
 
     *Vipul A M*
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index 501483498dc33e4eb727851a953e147f599fd400..686f12c6da07a853659a514af4964d3376fdacca 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -1,6 +1,5 @@
 require 'active_support/core_ext/hash/conversions'
 require 'active_support/core_ext/hash/deep_merge'
-require 'active_support/core_ext/hash/diff'
 require 'active_support/core_ext/hash/except'
 require 'active_support/core_ext/hash/indifferent_access'
 require 'active_support/core_ext/hash/keys'
diff --git a/activesupport/lib/active_support/core_ext/hash/diff.rb b/activesupport/lib/active_support/core_ext/hash/diff.rb
deleted file mode 100644
index 4359213380ee6778ee70c94ec4deec2f36f23f4f..0000000000000000000000000000000000000000
--- a/activesupport/lib/active_support/core_ext/hash/diff.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-require 'active_support/deprecation'
-
-class Hash
-  # Returns a hash that represents the difference between two hashes.
-  #
-  #   {1 => 2}.diff(1 => 2)         # => {}
-  #   {1 => 2}.diff(1 => 3)         # => {1 => 2}
-  #   {}.diff(1 => 2)               # => {1 => 2}
-  #   {1 => 2, 3 => 4}.diff(1 => 2) # => {3 => 4}
-  def diff(other)
-    ActiveSupport::Deprecation.warn "Hash#diff is no longer used inside of Rails, and is being deprecated with no replacement. If you're using it to compare hashes for the purpose of testing, please use MiniTest's assert_equal instead."
-    dup.
-      delete_if { |k, v| other[k] == v }.
-      merge!(other.dup.delete_if { |k, v| has_key?(k) })
-  end
-end
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index c6d7ab618cef56554d7fe90ffa02cf627e2eab8f..085779603658f44f0ba8942c7710664c22582334 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -701,12 +701,6 @@ def test_reverse_merge
     assert_equal expected, merged
   end
 
-  def test_diff
-    assert_deprecated do
-      assert_equal({ :a => 2 }, { :a => 2, :b => 5 }.diff({ :a => 1, :b => 5 }))
-    end
-  end
-
   def test_slice
     original = { :a => 'x', :b => 'y', :c => 10 }
     expected = { :a => 'x', :b => 'y' }