diff --git a/.changeset/forty-ears-rule.md b/.changeset/forty-ears-rule.md
new file mode 100644
index 000000000000..4369914db3ee
--- /dev/null
+++ b/.changeset/forty-ears-rule.md
@@ -0,0 +1,5 @@
+---
+'@graphql-codegen/schema-ast': minor
+---
+
+Allow .graphqls as extension
diff --git a/packages/plugins/other/schema-ast/src/index.ts b/packages/plugins/other/schema-ast/src/index.ts
index c696f954f2d8..2f593ce06e53 100644
--- a/packages/plugins/other/schema-ast/src/index.ts
+++ b/packages/plugins/other/schema-ast/src/index.ts
@@ -130,7 +130,7 @@ export const validate: PluginValidateFn<any> = async (
 ) => {
   const singlePlugin = allPlugins.length === 1;
 
-  const allowedExtensions = ['.graphql', '.gql'];
+  const allowedExtensions = ['.graphql', '.gql', '.graphqls'];
   const isAllowedExtension = allowedExtensions.includes(extname(outputFile));
 
   if (singlePlugin && !isAllowedExtension) {
diff --git a/packages/plugins/other/schema-ast/tests/schema-ast.spec.ts b/packages/plugins/other/schema-ast/tests/schema-ast.spec.ts
index 51637da84bcd..36e8e97631d7 100644
--- a/packages/plugins/other/schema-ast/tests/schema-ast.spec.ts
+++ b/packages/plugins/other/schema-ast/tests/schema-ast.spec.ts
@@ -22,7 +22,7 @@ describe('Schema AST', () => {
         throw new Error(SHOULD_THROW_ERROR);
       } catch (e) {
         expect(e.message).not.toBe(SHOULD_THROW_ERROR);
-        expect(e.message).toBe('Plugin "schema-ast" requires extension to be ".graphql" or ".gql"!');
+        expect(e.message).toBe('Plugin "schema-ast" requires extension to be ".graphql" or ".gql" or ".graphqls"!');
       }
     });
 
@@ -73,6 +73,21 @@ describe('Schema AST', () => {
         expect(true).toBeFalsy();
       }
     });
+
+    it('Should allow .graphqls extension when its the only plugin', async () => {
+      const fileName = 'output.graphqls';
+      const plugins: Types.ConfiguredPlugin[] = [
+        {
+          'schema-ast': {},
+        },
+      ];
+
+      try {
+        await validate(null, null, null, fileName, plugins);
+      } catch (e) {
+        expect(true).toBeFalsy();
+      }
+    });
   });
   describe('Output', () => {
     const typeDefs = /* GraphQL */ `