Although physical activity has numerous health benefits, only 12% of adults with physical disabilities participate regularly in leisure-time physical activity (LTPA) (Healthy People, 2010). Governmental agencies have called for theory-driven and contemporary LTPA motivational programs among such understudied populations as people with disabilities. However, most of the physical activity promotion studies have focused on physical activity behavior change among active individuals without disabilities. Additionally, few studies have explored the longitudinal effects of physical activity motivational programs. Therefore, the purpose of this study was to develop and assess both the short and long-term effects of a one-month web-based LTPA motivational program based on certain principles from the Transtheoretical Model (e.g., use of behavioral and cognitive strategies for LTPA behavior change). The program materials were tailored to mainly inactive adults with physical disabilities. This was a nationwide true experimental design, with one experimental and one control group. Participants were recruited through a study flyer that had been distributed to such disability sites as rehabilitation centers and hospitals. From the 151 individuals who completed the baseline assessment, 49 people (M age = 38.9 years; females = 77.6%; Caucasian = 86.7%) completed both the one-month post-intervention and 6-month follow-up LTPA questionnaire (Washburn et al., 2002). The main disability categories were spinal cord injury (30.6%), multiple sclerosis (26.5%), and cerebral palsy (18.4%). Using the LTPA baseline scores as a covariate, a one-way MANCOVA was conducted to identify differences between the treatment and control groups during post-intervention and at 6-month follow-up assessments. The study results confirmed the necessity to control for pretest LTPA scores at both post-intervention (F (1, 46) = 12.5, p = .001) and 6-month follow-up time periods (F (1, 46) = 37.94, p < .001). Additionally, the effects of the treatment were statistically significant only during post-intervention (F (1, 46) = 5.7, p = .02), whereby the treatment group increased their LTPA participation (MLTPA = ±9.5 MET hours/day) significantly more than the control group (MLTPA = ±3.9 MET hours/day). These findings support the short-term program efficacy. Specifically, positive LTPA behavior change for the treatment group occurred immediately after the intervention program. However, the long-term effects of the motivational program were not supported during the 6-month follow-up period. Future studies need to focus on both the short and long-term effects of theory-based and contemporary physical activity motivational programs among such understudied populations as people with disabilities.Keyword(s): health promotion, physical activity, research