Despite the proven benefits of physical activity to treat and prevent metabolic diseases, such as diabetes (T2D) and metabolic syndrome (MetS), most individuals with metabolic disease do not meet physical activity (PA) recommendations. PA is a complex behavior requiring substantial motivational and cognitive resources. The purpose of this study was to examine social cognitive and neuropsychological determinants of PA behavior in older adults with T2D and MetS. The hypothesized model theorized that baseline self-regulatory strategy use and cognitive function would indirectly influence PA through self-efficacy. Older adults with T2D or MetS (M age=61.8±6.4) completed either an 8-week physical activity intervention (n=58) or an online metabolic health education course (n=58) and a follow-up at 6months. Measures included cognitive function, self-efficacy, self-regulatory strategy use, and PA. The data partially supported the hypothesized model (χ2=158.535(131), p>.05, comparative fit index=.96, root mean square error of approximation=.04, standardized root mean square residual=.06) with self-regulatory strategy use directly predicting self-efficacy (β=.33, p<.05), which in turn predicted PA (β=.21, p<.05). Performance on various cognitive function tasks predicted PA directly and indirectly via self-efficacy. Baseline physical activity (β=.62, p<.01) and intervention group assignment via self-efficacy (β=-.20, p<.05) predicted follow-up PA. The model accounted for 54.4% of the variance in PA at month 6. Findings partially support the hypothesized model and indicate that select cognitive functions (i.e., working memory, inhibition, attention, and task-switching) predicted PA behavior 6months later. Future research warrants the development of interventions targeting cognitive function, self-regulatory skill development, and self-efficacy enhancement. The trial was registered with the clinical trial number NCT01790724.