diff --git a/toys/gapic/.toys.rb b/toys/gapic/.toys.rb
index b53209e0..77640678 100644
--- a/toys/gapic/.toys.rb
+++ b/toys/gapic/.toys.rb
@@ -15,6 +15,7 @@
 # limitations under the License.
 
 toys_version! ">= 0.15.3"
+require "bundler"
 
 expand :clean, paths: :gitignore
 
@@ -28,6 +29,29 @@
 
 tool "yard", delegate_to: "yardoc"
 
+tool "doctest" do
+  desc "Run yard-doctest example tests."
+
+  include :exec, e: true
+
+  def run
+    require "bundler"
+    unless File.exist? "support/doctest_helper.rb"
+      puts "No doctest helper present, skipping doctests."
+      exit 0
+    end
+    Dir.chdir context_directory
+    env_method = Bundler.respond_to?(:with_unbundled_env) ? :with_unbundled_env : :with_clean_env
+    Bundler.send env_method do
+      exec ["bundle", "exec", "yard", "config", "load_plugins", "true"]
+      patch_path = File.expand_path "doctest_mock_patch.rb", __dir__
+      rubyopt = [ENV["RUBYOPT"], "-r#{patch_path}"].compact.join " "
+      exec ["bundle", "exec", "yard", "doctest"], env: { "MT_KWARGS_HACK" => "1", "RUBYOPT" => rubyopt }
+    end
+  end
+end
+
+
 expand :gem_build
 
 expand :gem_build, name: "install", install_gem: true
@@ -45,7 +69,8 @@
 
   def run
     Dir.chdir context_directory
-    Bundler.with_clean_env do
+    env_method = Bundler.respond_to?(:with_unbundled_env) ? :with_unbundled_env : :with_clean_env
+    Bundler.send env_method do
       exec ["bundle", update ? "update" : "install"]
     end
   end
diff --git a/toys/gapic/ci.rb b/toys/gapic/ci.rb
index c4504896..2e1de0fd 100644
--- a/toys/gapic/ci.rb
+++ b/toys/gapic/ci.rb
@@ -19,6 +19,7 @@
   "rubocop" => [],
   "build" => [],
   "yard" => [],
+  "doctest" => [],
   "linkinator" => [],
   "acceptance" => [:project, :keyfile],
   "samples-main" => [:project, :keyfile, :samples_bundle_update],
diff --git a/toys/gapic/doctest_mock_patch.rb b/toys/gapic/doctest_mock_patch.rb
new file mode 100644
index 00000000..9f816d1f
--- /dev/null
+++ b/toys/gapic/doctest_mock_patch.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module Kernel
+  alias orig_require_for_doctest require
+  def require path
+    res = orig_require_for_doctest path
+    Kernel.patch_minitest_mock_if_needed!
+    res
+  end
+
+  class << self
+    alias orig_singleton_require_for_doctest require
+    def require path
+      res = orig_singleton_require_for_doctest path
+      Kernel.patch_minitest_mock_if_needed!
+      res
+    end
+
+    def patch_minitest_mock_if_needed!
+      return unless defined?(Minitest::Mock)
+      return if Minitest::Mock.instance_methods(false).include? :orig_expect_for_doctest
+      Minitest::Mock.class_eval do
+        alias orig_expect_for_doctest expect
+        def expect name, retval, args = [], **kwargs, &blk
+          args = args[0...-1] if args.is_a?(Array) && args.last == Hash
+          orig_expect_for_doctest name, retval, args, **kwargs, &blk
+        end
+
+        alias orig_method_missing_for_doctest method_missing
+        def method_missing sym, *args, **kwargs, &block
+          orig_method_missing_for_doctest sym, *args, **kwargs, &block
+        rescue ArgumentError => e
+          raise unless e.message.include? "keyword arguments"
+          orig_method_missing_for_doctest sym, *args, &block
+        end
+
+        def respond_to_missing? sym, include_private = false
+          super
+        end
+      end
+    end
+  end
+end
+
+Kernel.patch_minitest_mock_if_needed!