The goal of this pilot study was to compare Alexa voice and video interfaces for home-based telerehabilitation dialog by conducting cognitive walkthrough testing. All task performance scores were higher in video interface as compared to the audio interface. The overall task score was significantly higher for video interface (42.4±4.6) as compared to the audio score (41.3±5.9). Comparative usability survey demonstrated higher preference of the video interface as compared to the audio interface. Based in the comparative survey, 85.7% stated they definitely prefer video interface, 85.7% felt that video introduction was simpler to understand, 71.4% felt that exercise instructions were simpler to understand with the video interface, and 78.6% felt that overall navigation was easier with the video interface. The overall time to accomplish all three tasks was significantly shorter (p<0.05) for the video interface (170.5±12.2 seconds) as compared to the audio interface (194.2±10.3 seconds). This is the first study systematically comparing two major Alexa interfaces in a telerehabilitation system. These results are instrumental for future development of Alexa-based telerehabilitation systems.