diff --git a/lib/tapioca/dsl/compilers/active_record_fixtures.rb b/lib/tapioca/dsl/compilers/active_record_fixtures.rb
index a688b536e..01b44b224 100644
--- a/lib/tapioca/dsl/compilers/active_record_fixtures.rb
+++ b/lib/tapioca/dsl/compilers/active_record_fixtures.rb
@@ -26,6 +26,8 @@ module Compilers
       # # test_case.rbi
       # # typed: true
       # class ActiveSupport::TestCase
+      #   include ActiveRecord::TestFixtures
+      #
       #   sig { returns(T::Array[Post]) }                                                          #   No names: returns an Array of all fixtures
       #   sig { params(fixture_name: T.any(String, Symbol)).returns(Post) }                        #   One name: returns the requested fixture
       #   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)) # Many names: returns an Array of the requested fixtures
@@ -33,6 +35,12 @@ module Compilers
       #   def posts(fixture_name = nil, *other_fixtures); end
       # end
       # ~~~
+      #
+      # The `include` is generated because Rails mixes `ActiveRecord::TestFixtures` into
+      # `ActiveSupport::TestCase` through the `:active_support_test_case` load hook in
+      # `rails/test_help.rb`. Since RBI generation does not load an app's test helper, this runtime
+      # include is not captured. Without it, Sorbet does not see the class methods the module
+      # contributes via `mixes_in_class_methods`, such as `fixtures`.
       #: [ConstantType = singleton(ActiveSupport::TestCase)]
       class ActiveRecordFixtures < Compiler
         MISSING = Object.new
@@ -47,9 +55,10 @@ def decorate
           end
 
           method_names.select! { |name| fixture_class_mapping_from_fixture_files[name] != MISSING }
-          return if method_names.empty?
 
           root.create_path(constant) do |mod|
+            mod.create_include("ActiveRecord::TestFixtures")
+
             method_names.each do |name|
               create_fixture_method(mod, name.to_s)
             end
diff --git a/manual/compiler_activerecordfixtures.md b/manual/compiler_activerecordfixtures.md
index b34fbf4db..74a35a33f 100644
--- a/manual/compiler_activerecordfixtures.md
+++ b/manual/compiler_activerecordfixtures.md
@@ -18,6 +18,8 @@ The generated RBI by this compiler will produce the following
 # test_case.rbi
 # typed: true
 class ActiveSupport::TestCase
+  include ActiveRecord::TestFixtures
+
   sig { returns(T::Array[Post]) }                                                          #   No names: returns an Array of all fixtures
   sig { params(fixture_name: T.any(String, Symbol)).returns(Post) }                        #   One name: returns the requested fixture
   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)) # Many names: returns an Array of the requested fixtures
@@ -25,3 +27,9 @@ class ActiveSupport::TestCase
   def posts(fixture_name = nil, *other_fixtures); end
 end
 ~~~
+
+The `include` is generated because Rails mixes `ActiveRecord::TestFixtures` into
+`ActiveSupport::TestCase` through the `:active_support_test_case` load hook in
+`rails/test_help.rb`. Since RBI generation does not load an app's test helper, this runtime
+include is not captured. Without it, Sorbet does not see the class methods the module contributes
+via `mixes_in_class_methods`, such as `fixtures`.
diff --git a/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb b/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb
index dd72389ea..73f2d4400 100644
--- a/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb
+++ b/spec/tapioca/dsl/compilers/active_record_fixtures_spec.rb
@@ -47,12 +47,42 @@ class User
               assert_equal(["ActiveSupport::TestCase"], gathered_constants)
             end
 
-            it "does nothing if there are no fixtures" do
+            it "makes fixture class methods available when there are no fixtures" do
               expected = <<~RBI
                 # typed: strong
+
+                class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+                end
               RBI
 
-              assert_equal(expected, rbi_for("ActiveSupport::TestCase"))
+              generated_rbi = rbi_for("ActiveSupport::TestCase")
+              dependencies_rbi = add_content_file("dependencies.rbi", <<~RBI)
+                # typed: true
+
+                module ActiveRecord::TestFixtures
+                  mixes_in_class_methods ::ActiveRecord::TestFixtures::ClassMethods
+                end
+
+                module ActiveRecord::TestFixtures::ClassMethods
+                  def fixtures(*fixture_set_names); end
+                end
+
+                class ActiveSupport::TestCase; end
+              RBI
+              generated_rbi_file = add_content_file("generated.rbi", generated_rbi)
+              test_file = add_content_file("test_case.rb", <<~RUBY)
+                # typed: true
+
+                class PostTest < ActiveSupport::TestCase
+                  fixtures :all
+                end
+              RUBY
+
+              result = context.sorbet("--no-config", dependencies_rbi, generated_rbi_file, test_file)
+
+              assert(result.status, result.err)
+              assert_equal(expected, generated_rbi)
             end
 
             it "ignores fixtures that do not have an associated model" do
@@ -79,6 +109,8 @@ class Post < ActiveRecord::Base
                 # typed: strong
 
                 class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+
                   sig { returns(T::Array[Post]) }
                   sig { params(fixture_name: T.any(String, Symbol)).returns(Post) }
                   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)).returns(T::Array[Post]) }
@@ -89,6 +121,24 @@ def posts(fixture_name = nil, *other_fixtures); end
               assert_equal(expected, rbi_for("ActiveSupport::TestCase"))
             end
 
+            it "generates only the include if no fixture has an associated model" do
+              add_content_file("test/fixtures/serialized_data.yml", <<~YAML)
+                ---
+                field1: 123
+                name: Hello
+              YAML
+
+              expected = <<~RBI
+                # typed: strong
+
+                class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+                end
+              RBI
+
+              assert_equal(expected, rbi_for("ActiveSupport::TestCase"))
+            end
+
             it "generates methods for fixtures" do
               add_content_file("test/fixtures/posts.yml", <<~YAML)
                 super_post:
@@ -107,6 +157,8 @@ class Post < ActiveRecord::Base
                 # typed: strong
 
                 class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+
                   sig { returns(T::Array[Post]) }
                   sig { params(fixture_name: T.any(String, Symbol)).returns(Post) }
                   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)).returns(T::Array[Post]) }
@@ -146,6 +198,8 @@ class User < ActiveRecord::Base
                 # typed: strong
 
                 class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+
                   sig { returns(T::Array[Blog::Post]) }
                   sig { params(fixture_name: T.any(String, Symbol)).returns(Blog::Post) }
                   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)).returns(T::Array[Blog::Post]) }
@@ -181,6 +235,8 @@ class Post < ActiveRecord::Base
                 # typed: strong
 
                 class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+
                   sig { returns(T::Array[Post]) }
                   sig { params(fixture_name: T.any(String, Symbol)).returns(Post) }
                   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)).returns(T::Array[Post]) }
@@ -204,6 +260,8 @@ def posts_with_other_names(fixture_name = nil, *other_fixtures); end
                 # typed: strong
 
                 class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+
                   sig { returns(T::Array[T.untyped]) }
                   sig { params(fixture_name: T.any(String, Symbol)).returns(T.untyped) }
                   sig { params(fixture_name: T.any(String, Symbol), other_fixtures: T.any(String, Symbol)).returns(T::Array[T.untyped]) }
@@ -214,7 +272,7 @@ def posts(fixture_name = nil, *other_fixtures); end
               assert_equal(expected, rbi_for("ActiveSupport::TestCase"))
             end
 
-            it "generates no methods for file fixtures" do
+            it "generates only the include for file fixtures" do
               add_content_file("test/fixtures/files/posts.yml", <<~YAML)
                 super_post:
                   title: An incredible Ruby post
@@ -225,6 +283,10 @@ def posts(fixture_name = nil, *other_fixtures); end
 
               expected = <<~RBI
                 # typed: strong
+
+                class ActiveSupport::TestCase
+                  include ActiveRecord::TestFixtures
+                end
               RBI
 
               assert_equal(expected, rbi_for("ActiveSupport::TestCase"))