diff --git a/lib/devise.rb b/lib/devise.rb
index d4d54aeb..6ccbbc3d 100644
--- a/lib/devise.rb
+++ b/lib/devise.rb
@@ -305,6 +305,10 @@ module Devise
     defined?(ActiveRecord) && ActiveRecord.gem_version >= Gem::Version.new("5.1.x")
   end
 
+  def self.rails6_and_up?
+    Rails.gem_version >= Gem::Version.new("6.0.x")
+  end
+
   # Default way to set up Devise. Run rails generate devise_install to create
   # a fresh initializer with all configuration values.
   def self.setup
diff --git a/lib/devise/rails.rb b/lib/devise/rails.rb
index 5cc5fa6d..34bc3644 100644
--- a/lib/devise/rails.rb
+++ b/lib/devise/rails.rb
@@ -43,5 +43,11 @@ module Devise
           )
         end
     end
+
+    initializer "devise.zeitwerk" do
+      if Devise.rails6_and_up? && Rails.autoloaders.zeitwerk_enabled? && !Object.const_defined?(Devise.parent_mailer)
+        Rails.autoloaders.main.ignore("#{__dir__}/app/mailers/devise/mailer.rb")
+      end
+    end
   end
 end
diff --git a/test/rails_app/config/application.rb b/test/rails_app/config/application.rb
index 0c844878..465d6287 100644
--- a/test/rails_app/config/application.rb
+++ b/test/rails_app/config/application.rb
@@ -49,5 +49,9 @@ module RailsApp
     if Devise::Test.rails52_and_up? && !Devise::Test.rails6?
       Rails.application.config.active_record.sqlite3.represent_boolean_as_integer = true
     end
+
+    if Devise.rails6_and_up?
+      config.autoloader = :zeitwerk
+    end
   end
 end
diff --git a/test/rails_test.rb b/test/rails_test.rb
index fdc1612e..2317bbf2 100644
--- a/test/rails_test.rb
+++ b/test/rails_test.rb
@@ -8,4 +8,24 @@ class RailsTest < ActiveSupport::TestCase
     assert_equal :load_config_initializers, initializer.after
     assert_equal :build_middleware_stack, initializer.before
   end
+
+  test 'ignore devise mailer loading when ActionMailer is not defined with zeitwerk' do
+    if Devise.rails6_and_up?
+      begin
+        swap Devise, parent_mailer: 'NotDefinedParentMailer' do
+          Devise::Engine.initializers.detect { |initializer| initializer.name == 'devise.zeitwerk' }.block.call
+          assert Rails.autoloaders.main.ignored_glob_patterns.any? { |pattern| pattern.include?("mailer.rb") }
+        end
+      ensure
+        Rails.autoloaders.main.instance_variable_set(:@ignored_glob_patterns, Set.new)
+      end
+    end
+  end
+
+  test 'load devise mailer file when Devise.parent_mailer is defined with zeitwerk' do
+    if Devise.rails6_and_up?
+      Devise::Engine.initializers.detect { |initializer| initializer.name == 'devise.zeitwerk' }.block.call
+      refute Rails.autoloaders.main.ignored_glob_patterns.any? { |pattern| pattern.include?("mailer.rb") }
+    end
+  end
 end