diff --git a/changelog/fix_an_error_for_rails_action_controller_flash_before_render.md b/changelog/fix_an_error_for_rails_action_controller_flash_before_render.md
new file mode 100644
index 0000000000..03ec9d040b
--- /dev/null
+++ b/changelog/fix_an_error_for_rails_action_controller_flash_before_render.md
@@ -0,0 +1 @@
+* [#1539](https://github.com/rubocop/rubocop-rails/issues/1539): Fix an error in `Rails/ActionControllerFlashBeforeRender` when `flash` is used inside a block followed by method chaining. ([@koic][])
diff --git a/lib/rubocop/cop/rails/action_controller_flash_before_render.rb b/lib/rubocop/cop/rails/action_controller_flash_before_render.rb
index bab9011c94..9980e1ee41 100644
--- a/lib/rubocop/cop/rails/action_controller_flash_before_render.rb
+++ b/lib/rubocop/cop/rails/action_controller_flash_before_render.rb
@@ -98,7 +98,9 @@ def instance_method_or_block?(node)
         end
 
         def use_redirect_to?(context)
-          context.right_siblings.compact.any? do |sibling|
+          context.right_siblings.any? do |sibling|
+            next unless sibling.is_a?(AST::Node)
+
             # Unwrap `return redirect_to :index`
             sibling = sibling.children.first if sibling.return_type? && sibling.children.one?
             sibling.send_type? && sibling.method?(:redirect_to)
diff --git a/spec/rubocop/cop/rails/action_controller_flash_before_render_spec.rb b/spec/rubocop/cop/rails/action_controller_flash_before_render_spec.rb
index fa1e45097f..3a8a662484 100644
--- a/spec/rubocop/cop/rails/action_controller_flash_before_render_spec.rb
+++ b/spec/rubocop/cop/rails/action_controller_flash_before_render_spec.rb
@@ -427,4 +427,16 @@ def create
       RUBY
     end
   end
+
+  context 'when `flash` is used inside a block followed by method chaining' do
+    it 'does not register an offense and corrects' do
+      expect_no_offenses(<<~RUBY)
+        class NonController < ApplicationRecord
+          before_action do
+            flash[:notice] = 'hello'
+          end.do_something
+        end
+      RUBY
+    end
+  end
 end