diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 17617206cb..67f117454f 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,11 @@
+*   Use the Active Support JSON encoder for cookie jars using the `:json` or
+    `:hybrid` serializer. This allows you to serialize custom Ruby objects into
+    cookies by defining the `#as_json` hook on such objects.
+
+    Fixes #16520.
+
+    *Godfrey Chan*
+
 *   Add `config.action_dispatch.cookies_digest` option for setting custom
     digest. The default remains the same - 'SHA1'.
 
diff --git a/actionpack/lib/action_dispatch/middleware/cookies.rb b/actionpack/lib/action_dispatch/middleware/cookies.rb
index 5b3c0e7316..83ac62a83d 100644
--- a/actionpack/lib/action_dispatch/middleware/cookies.rb
+++ b/actionpack/lib/action_dispatch/middleware/cookies.rb
@@ -3,6 +3,7 @@ require 'active_support/core_ext/module/attribute_accessors'
 require 'active_support/core_ext/object/blank'
 require 'active_support/key_generator'
 require 'active_support/message_verifier'
+require 'active_support/json'
 
 module ActionDispatch
   class Request < Rack::Request
@@ -391,11 +392,11 @@ module ActionDispatch
 
     class JsonSerializer
       def self.load(value)
-        JSON.parse(value, quirks_mode: true)
+        ActiveSupport::JSON.decode(value)
       end
 
       def self.dump(value)
-        JSON.generate(value, quirks_mode: true)
+        ActiveSupport::JSON.encode(value)
       end
     end
 
diff --git a/actionpack/test/dispatch/cookies_test.rb b/actionpack/test/dispatch/cookies_test.rb
index 7e7dd94425..9b03c805a0 100644
--- a/actionpack/test/dispatch/cookies_test.rb
+++ b/actionpack/test/dispatch/cookies_test.rb
@@ -21,6 +21,16 @@ class CookiesTest < ActionController::TestCase
     end
   end
 
+  class JSONWrapper
+    def initialize(obj)
+      @obj = obj
+    end
+
+    def as_json(options = nil)
+      "wrapped: #{@obj.as_json(options)}"
+    end
+  end
+
   class TestController < ActionController::Base
     def authenticate
       cookies["user_name"] = "david"
@@ -85,6 +95,11 @@ class CookiesTest < ActionController::TestCase
       head :ok
     end
 
+    def set_wrapped_signed_cookie
+      cookies.signed[:user_id] = JSONWrapper.new(45)
+      head :ok
+    end
+
     def get_signed_cookie
       cookies.signed[:user_id]
       head :ok
@@ -95,6 +110,11 @@ class CookiesTest < ActionController::TestCase
       head :ok
     end
 
+    def set_wrapped_encrypted_cookie
+      cookies.encrypted[:foo] = JSONWrapper.new('bar')
+      head :ok
+    end
+
     def get_encrypted_cookie
       cookies.encrypted[:foo]
       head :ok
@@ -421,6 +441,14 @@ class CookiesTest < ActionController::TestCase
     assert_equal 45, cookies.signed[:user_id]
   end
 
+  def test_wrapped_signed_cookie_using_json_serializer
+    @request.env["action_dispatch.cookies_serializer"] = :json
+    get :set_wrapped_signed_cookie
+    cookies = @controller.send :cookies
+    assert_not_equal 'wrapped: 45', cookies[:user_id]
+    assert_equal 'wrapped: 45', cookies.signed[:user_id]
+  end
+
   def test_signed_cookie_using_custom_serializer
     @request.env["action_dispatch.cookies_serializer"] = CustomSerializer
     get :set_signed_cookie
@@ -503,6 +531,17 @@ class CookiesTest < ActionController::TestCase
     assert_equal 'bar', cookies.encrypted[:foo]
   end
 
+  def test_wrapped_encrypted_cookie_using_json_serializer
+    @request.env["action_dispatch.cookies_serializer"] = :json
+    get :set_wrapped_encrypted_cookie
+    cookies = @controller.send :cookies
+    assert_not_equal 'wrapped: bar', cookies[:foo]
+    assert_raises ::JSON::ParserError do
+      cookies.signed[:foo]
+    end
+    assert_equal 'wrapped: bar', cookies.encrypted[:foo]
+  end
+
   def test_encrypted_cookie_using_custom_serializer
     @request.env["action_dispatch.cookies_serializer"] = CustomSerializer
     get :set_encrypted_cookie