Usability is an important topic in the field of telerehabilitation research. Older users with disabilities in particular, present age-related and disability-related challenges that should be accommodated for in the design of a user interface for a telerehabilitation system. This paper describes the design, implementation, and assessment of a telerehabilitation system user interface that tries to maximize usability for an elderly user who has experienced a stroke. An Internet-connected Nintendo(®) Wii™ gaming system is selected as a hardware platform, and a server and website are implemented to process and display the feedback information. The usability of the interface is assessed with a trial consisting of 18 subjects: 10 healthy Doctor of Physical Therapy students and 8 people with a stroke. Results show similar levels of usability and high satisfaction with the gaming system interface from both groups of subjects.