Adults with serious mental illness (SMI) engage in limited physical activity and are more sedentary than the general population. This contributes to significant health disparities and premature mortality in this population due in large part to cardiovascular disease. We proposed using ecological momentary assessment (EMA) through mobile phone technology to understand physical activity patterns of 30 participants currently enrolled in an integrated physical and behavioral healthcare program for Latino Adults with SMI. EMA is a real-time data capture strategy, which allows participants to report their current mood, mental health symptoms, activity, location, and social surroundings at any particular moment. Participants wore an accelerometer that serves as an objective measure of activity level was monitored across 4 days (Saturday–Tuesday) between 6:30am and 10:00pm. Eight EMA surveys were prompted per day. Each EMA survey was prompted at a random time within eight pre-programmed windows in order to capture time-sensitive promoters of physical activity, which can form the basis of lifestyle interventions. The intent of the pilot was to test the feasibility, acceptability, and validity of a real-time EMA protocol using self-report electronic surveys as well as to identify potential ways to intervene through follow-up participant focus groups in which the results of the pilot were presented.