diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 3d3015ad07..25ec3cf5b6 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -144,16 +144,21 @@ module ActionController
     end
 
     # Returns true if another +Parameters+ object contains the same content and
-    # permitted flag, or other Hash-like object contains the same content.
-    def ==(other_hash)
-      if other_hash.respond_to?(:permitted?)
-        self.permitted? == other_hash.permitted? && self.parameters == other_hash.parameters
+    # permitted flag.
+    def ==(other)
+      if other.respond_to?(:permitted?)
+        self.permitted? == other.permitted? && self.parameters == other.parameters
+      elsif other.is_a?(Hash)
+        ActiveSupport::Deprecation.warn <<-WARNING.squish
+          Comparing equality between `ActionController::Parameters` and a
+          `Hash` is deprecated and will be removed in Rails 5.1. Please only do
+          comparisons between instances of `ActionController::Parameters`. If
+          you need to compare to a hash, first convert it using
+          `ActionController::Parameters#new`.
+        WARNING
+        @parameters == other.with_indifferent_access
       else
-        if other_hash.is_a?(Hash)
-          @parameters == other_hash.with_indifferent_access
-        else
-          @parameters == other_hash
-        end
+        @parameters == other
       end
     end
 
diff --git a/actionpack/test/controller/parameters/accessors_test.rb b/actionpack/test/controller/parameters/accessors_test.rb
index ef8eb5f33e..4ef5bed30d 100644
--- a/actionpack/test/controller/parameters/accessors_test.rb
+++ b/actionpack/test/controller/parameters/accessors_test.rb
@@ -129,10 +129,12 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     assert_not @params[:person].values_at(:name).first.permitted?
   end
 
-  test "equality with another hash works" do
+  test "equality with a hash is deprecated" do
     hash1 = { foo: :bar }
     params1 = ActionController::Parameters.new(hash1)
-    assert(params1 == hash1)
+    assert_deprecated("will be removed in Rails 5.1") do
+      assert(params1 == hash1)
+    end
   end
 
   test "is equal to Parameters instance with same params" do