Most people do not engage in recommended levels of physical activity. Social cognition research indicates that self-reported outcome expectancies (OEs) are associated with exercise behavior, but self-report assessments have limitations. We investigated whether reaction times (RTs) to endorse outcome expectancies would capture unique information about spontaneous cognitive processes associated with exercise behavior. Exercisers and sedentary participants were randomly assigned to complete an exercise test or to rest. Participants completed an OE questionnaire and RT task before and after the test/rest. On the RT task, exercisers endorsed exercise positive outcomes more rapidly than sedentary participants. Furthermore, reported OEs and RTs were independently associated with exercise status. RTs may afford a more comprehensive assessment of the cognitive processes associated with exercise behavior.