diff --git a/src/jsc/bindings/JSMockFunction.cpp b/src/jsc/bindings/JSMockFunction.cpp
index 1c1c7fe70f6..2aa6f6b9bd1 100644
--- a/src/jsc/bindings/JSMockFunction.cpp
+++ b/src/jsc/bindings/JSMockFunction.cpp
@@ -86,6 +86,7 @@ inline To tryJSDynamicCast(JSC::WriteBarrier<WriteBarrierT>& from)
 }
 
 JSC_DECLARE_HOST_FUNCTION(jsMockFunctionCall);
+JSC_DECLARE_HOST_FUNCTION(jsMockFunctionConstruct);
 JSC_DECLARE_CUSTOM_GETTER(jsMockFunctionGetter_protoImpl);
 JSC_DECLARE_CUSTOM_GETTER(jsMockFunctionGetter_mock);
 JSC_DECLARE_HOST_FUNCTION(jsMockFunctionGetter_mockGetLastCall);
@@ -462,7 +463,7 @@ class JSMockFunction : public JSC::InternalFunction {
     }
 
     JSMockFunction(JSC::VM& vm, JSC::Structure* structure, CallbackKind wrapKind)
-        : Base(vm, structure, jsMockFunctionCall, jsMockFunctionCall)
+        : Base(vm, structure, jsMockFunctionCall, jsMockFunctionConstruct)
     {
         initMock();
     }
@@ -826,7 +827,7 @@ static JSValue createMockResult(JSC::VM& vm, Zig::GlobalObject* globalObject, co
     return result;
 }
 
-JSC_DEFINE_HOST_FUNCTION(jsMockFunctionCall, (JSGlobalObject * lexicalGlobalObject, CallFrame* callframe))
+static JSC::EncodedJSValue jsMockFunctionCallImpl(JSGlobalObject* lexicalGlobalObject, CallFrame* callframe, JSValue thisValue)
 {
     Zig::GlobalObject* globalObject = uncheckedDowncast<Zig::GlobalObject>(lexicalGlobalObject);
     auto& vm = JSC::getVM(globalObject);
@@ -838,7 +839,6 @@ JSC_DEFINE_HOST_FUNCTION(jsMockFunctionCall, (JSGlobalObject * lexicalGlobalObje
     }
 
     JSC::ArgList args = JSC::ArgList(callframe);
-    JSValue thisValue = callframe->thisValue();
     JSC::JSArray* argumentsArray = nullptr;
     {
         JSC::ObjectInitializationScope object(vm);
@@ -981,6 +981,38 @@ JSC_DEFINE_HOST_FUNCTION(jsMockFunctionCall, (JSGlobalObject * lexicalGlobalObje
     return JSValue::encode(jsUndefined());
 }
 
+JSC_DEFINE_HOST_FUNCTION(jsMockFunctionCall, (JSGlobalObject * lexicalGlobalObject, CallFrame* callframe))
+{
+    return jsMockFunctionCallImpl(lexicalGlobalObject, callframe, callframe->thisValue());
+}
+
+JSC_DEFINE_HOST_FUNCTION(jsMockFunctionConstruct, (JSGlobalObject * lexicalGlobalObject, CallFrame* callframe))
+{
+    auto& vm = JSC::getVM(lexicalGlobalObject);
+    auto scope = DECLARE_THROW_SCOPE(vm);
+
+    // For constructors implemented in C++, the this value slot holds new.target.
+    JSValue newTarget = callframe->newTarget();
+    JSObject* prototype = nullptr;
+    if (newTarget && newTarget.isObject()) {
+        JSValue prototypeValue = asObject(newTarget)->get(lexicalGlobalObject, vm.propertyNames->prototype);
+        RETURN_IF_EXCEPTION(scope, {});
+        if (prototypeValue.isObject())
+            prototype = asObject(prototypeValue);
+    }
+
+    JSObject* thisObject = prototype ? JSC::constructEmptyObject(lexicalGlobalObject, prototype) : JSC::constructEmptyObject(lexicalGlobalObject);
+
+    JSValue result = JSValue::decode(jsMockFunctionCallImpl(lexicalGlobalObject, callframe, thisObject));
+    RETURN_IF_EXCEPTION(scope, {});
+
+    // [[Construct]] must return an object, so fall back to the newly created
+    // instance when the mock implementation produced a primitive.
+    if (result && result.isObject())
+        return JSValue::encode(result);
+    return JSValue::encode(thisObject);
+}
+
 void JSMockFunctionPrototype::finishCreation(JSC::VM& vm, JSC::JSGlobalObject* globalObject)
 {
     Base::finishCreation(vm);
diff --git a/test/js/bun/test/mock-fn.test.js b/test/js/bun/test/mock-fn.test.js
index 7f6a244d980..f180b299dbb 100644
--- a/test/js/bun/test/mock-fn.test.js
+++ b/test/js/bun/test/mock-fn.test.js
@@ -1015,3 +1015,39 @@ describe("spyOn", () => {
 
   // spyOn does not work with getters/setters yet.
 });
+
+describe("mock constructor calls", () => {
+  test("constructing a mock with no implementation returns an object", () => {
+    const fn = jest.fn();
+    const instance = new fn();
+    expect(typeof instance).toBe("object");
+    expect(typeof Reflect.construct(fn, [])).toBe("object");
+    expect(fn.mock.contexts[0]).toBe(instance);
+  });
+
+  test("constructing a mock whose implementation returns a primitive returns an object", () => {
+    const fn = jest.fn(() => 42);
+    expect(typeof new fn()).toBe("object");
+    expect(typeof Reflect.construct(fn, [])).toBe("object");
+    expect(fn.mock.results).toEqual([
+      { type: "return", value: 42 },
+      { type: "return", value: 42 },
+    ]);
+  });
+
+  test("constructing a mock whose implementation returns an object returns that object", () => {
+    const obj = { a: 1 };
+    const fn = jest.fn(() => obj);
+    expect(new fn()).toBe(obj);
+    expect(Reflect.construct(fn, [])).toBe(obj);
+  });
+
+  if (isBun) {
+    test("constructing a spy on a missing property does not crash", () => {
+      const target = {};
+      const spy = spyOn(target, "doesNotExist");
+      expect(typeof Reflect.construct(spy, [])).toBe("object");
+      spy.mockRestore();
+    });
+  }
+});