In order to develop easy-to-use multimodal interfaces for mobile applications, effective usability evaluation methods (UEMs) are an essential component of the development process. Over the past decades various usability evaluation methods have been developed and implemented to improve and assure easyto-use user interfaces and systems. However, most of the so-called 'classical' methods exhibit shortcomings when used in the field of mobile applications, especially when addressing multimodal interaction (MMI). Hence, several 'classical' methods were broadened, varied, and changed to meet the demands of testing usability for multimodal interfaces and mobile applications. This chapter presents a selection of these 'classical' methods, and introduces some newly developed methods for testing usability in the area of multimodal interfaces. The chapter concludes with a summary on currently available methods for usability evaluation of multimodal interfaces for mobile devices.