diff --git a/changelog/new_enable_global_active_support_extensions_enabled_option.md b/changelog/new_enable_global_active_support_extensions_enabled_option.md
new file mode 100644
index 0000000000..4270479094
--- /dev/null
+++ b/changelog/new_enable_global_active_support_extensions_enabled_option.md
@@ -0,0 +1 @@
+* [#746](https://github.com/rubocop/rubocop-rails/pull/746): Enable `ActiveSupportExtensionsEnabled` option by default. ([@koic][])
diff --git a/config/default.yml b/config/default.yml
index 27446c2fed..7c886526eb 100644
--- a/config/default.yml
+++ b/config/default.yml
@@ -10,6 +10,9 @@ AllCops:
     # Exclude db/schema.rb and db/[CONFIGURATION_NAMESPACE]_schema.rb by default.
     # See: https://guides.rubyonrails.org/active_record_multiple_databases.html#setting-up-your-application
     - db/*schema.rb
+  # Enable checking Active Support extensions.
+  # See: https://docs.rubocop.org/rubocop/configuration.html#enable-checking-active-support-extensions
+  ActiveSupportExtensionsEnabled: true
   # What version of Rails is the inspected code using?  If a value is specified
   # for TargetRailsVersion then it is used.  Acceptable values are specified
   # as a float (i.e. 5.1); the patch version of Rails should not be included.