Spasticity after stroke is a common occurrence and requires treatment with rehabilitative regimens (e.g., stretching exercise). Unfortunately, many challenges (e.g., cost, limited availability of physical therapists, limited access to clinical facilities, etc.) can restrict participation in these rehabilitation regimens. Assistive technologies using robotic systems have been developed to provide an alternative to assist with rehabilitative exercises. However, existing assistive technologies are rarely available in clinical settings due to technical limitations (e.g., size, weight, complexity, etc.). This paper describes the development of a novel ankle rehabilitation system, called Motorized Ankle Stretcher (MAS). A proof-of-concept experiment was conducted to assess the effects of ankle stretching exercises with the MAS in a laboratory setting. Six stroke survivors participated in the proof-of-concept experiment. The participants' ankle range of motion (ROM) and walking performance (i.e., walking speed, step length, and cadence) were evaluated before and after a small number of the ankle stretching exercises using the MAS (i.e., 20 trials total) in a single training session. The results show that the ankle ROM was significantly increased after the exercises across all participants. However, no significant differences in walking speed, step length, and cadence were observed between pre- and post-exercises. Our investigation is a first attempt at developing a relatively small size, weight, and easy-to-use ankle rehabilitation system for stroke survivors.