diff --git a/.changeset/hot-trees-talk.md b/.changeset/hot-trees-talk.md
new file mode 100644
index 0000000000..2955d579bf
--- /dev/null
+++ b/.changeset/hot-trees-talk.md
@@ -0,0 +1,5 @@
+---
+'@sap-cloud-sdk/openapi-generator': minor
+---
+
+[Fix] Prevent query parameters from being optional when header parameters are required in signature.
diff --git a/packages/openapi-generator/src/file-serializer/operation.spec.ts b/packages/openapi-generator/src/file-serializer/operation.spec.ts
index 5cef761839..8b34637ceb 100644
--- a/packages/openapi-generator/src/file-serializer/operation.spec.ts
+++ b/packages/openapi-generator/src/file-serializer/operation.spec.ts
@@ -249,6 +249,71 @@ describe('serializeOperation', () => {
     `);
   });
 
+  it('serializes operation with optional query and optional + required header parameters', () => {
+    const operation: OpenApiOperation = {
+      operationId: 'getFn',
+      method: 'get',
+      tags: [],
+      pathParameters: [],
+      queryParameters: [
+        {
+          in: 'query',
+          name: 'limit',
+          originalName: 'limit',
+          schema: { type: 'number' },
+          schemaProperties: {},
+          required: false
+        },
+        {
+          in: 'query',
+          name: 'page',
+          originalName: 'page',
+          schema: { type: 'number' },
+          schemaProperties: {},
+          required: false
+        }
+      ],
+      headerParameters: [
+        {
+          in: 'header',
+          name: 'authentication',
+          originalName: 'authentication',
+          schema: { type: 'string' },
+          schemaProperties: {},
+          required: true
+        },
+        {
+          in: 'header',
+          name: 'resource-group',
+          originalName: 'resource-group',
+          schema: { type: 'string' },
+          schemaProperties: {},
+          required: false
+        }
+      ],
+      responses: { 200: { description: 'some response description' } },
+      response: { type: 'any' },
+      pathPattern: 'test'
+    };
+
+    expect(serializeOperation(operation)).toMatchInlineSnapshot(`
+      "/**
+       * Create a request builder for execution of get requests to the 'test' endpoint.
+       * @param queryParameters - Object containing the following keys: limit, page.
+       * @param headerParameters - Object containing the following keys: authentication, resource-group.
+       * @returns The request builder, use the \`execute()\` method to trigger the request.
+       */
+      getFn: (queryParameters: {'limit'?: number, 'page'?: number}, headerParameters: {'authentication': string, 'resource-group'?: string}) => new OpenApiRequestBuilder<any>(
+        'get',
+        "test",
+        {
+              queryParameters,
+              headerParameters
+            }
+      )"
+    `);
+  });
+
   it('serializes operation with required query and optional header parameters', () => {
     const operation: OpenApiOperation = {
       operationId: 'getFn',
diff --git a/packages/openapi-generator/src/file-serializer/operation.ts b/packages/openapi-generator/src/file-serializer/operation.ts
index 73484369d0..51dad2cd3f 100644
--- a/packages/openapi-generator/src/file-serializer/operation.ts
+++ b/packages/openapi-generator/src/file-serializer/operation.ts
@@ -36,15 +36,24 @@ ${operation.operationId}: (${serializeOperationSignature(
 function serializeOperationSignature(operation: OpenApiOperation): string {
   const pathParams = serializePathParamsForSignature(operation);
   const requestBodyParam = serializeRequestBodyParamForSignature(operation);
+
+  const allOptionalHeaders = operation.headerParameters.every(
+    param => !param.required
+  );
+  const allOptionalQuery = operation.queryParameters.every(
+    param => !param.required
+  );
+
   const headerParams = serializeParamsForSignature(
     operation,
-    'headerParameters'
+    'headerParameters',
+    allOptionalHeaders
   );
 
   const queryParams = serializeParamsForSignature(
     operation,
     'queryParameters',
-    headerParams?.includes('?')
+    allOptionalHeaders && allOptionalQuery
   );
 
   return [pathParams, requestBodyParam, queryParams, headerParams]
@@ -75,7 +84,7 @@ function serializeRequestBodyParamForSignature(
 function serializeParamsForSignature(
   operation: OpenApiOperation,
   paramType: 'queryParameters' | 'headerParameters',
-  canBeAllOptional = true
+  isAllOptional: boolean
 ): string | undefined {
   const parameters = operation[paramType];
   if (parameters.length) {
@@ -88,10 +97,7 @@ function serializeParamsForSignature(
       )
       .join(', ');
 
-    const allOptional = parameters.every(param => !param.required);
-    const optionalModifier = allOptional && canBeAllOptional ? '?' : '';
-
-    return `${paramType}${optionalModifier}: {${paramsString}}`;
+    return `${paramType}${isAllOptional ? '?' : ''}: {${paramsString}}`;
   }
 }