The study’s purpose was to identify the mediating role of intention and the stages of change (SOC) in physical activity (PA) over a 6-month period using two models (Theory of Planned Behavior [TPB] and TPB/SOC). Participants were 143 adults with physical disabilities (70.68% response rate; M age = 46.03). The TPB constructs, SOC (time 1), and PA (time 2) were assessed using standardized self-report questionnaires. Based on path analyses, attitude had the highest effect on intention and SOC followed by perceived behavioral control within both well-fit models. The variance in PA explained by the first (TPB) and second (TPB/SOC) models was 16% and 28% respectively. In the just identified model of TPB/SOC, the direct effect of SOC on physical activity remained strong (γsoc.pa = .45) and SOC approached full mediation through attitude. Health promotion interventions need to include both intention and behavior elements (SOC) reinforcing increased PA value and barrier elimination.