Physical activity reduces risk for numerous negative health outcomes, but postmenopausal breast cancer survivors do not reach recommended levels. Many interventions encourage self-monitoring of steps, which can increase physical activity in the short term. However, these interventions appear insufficient to increase motivation for sustained change. There is a need for innovative strategies to increase physical activity motivation in this population. Narratives are uniquely persuasive, and video games show promise for increasing motivation. This study will determine the effectiveness of an intervention that combines narrative and gaming to encourage sustained physical activity. SMARTGOAL (Self-Monitoring Activity: a Randomized Trial of Game-Oriented AppLications) is a randomized controlled intervention trial. The intervention period is six months, followed by a six month maintenance period. Participants (overweight, sedentary postmenopausal breast cancer survivors aged 45-75) will be randomized to a self-monitoring group or an enhanced narrative game group. The self-monitoring group will be encouraged to use a mobile application for self-monitoring and feedback and will receive 15 counseling phone calls emphasizing self-regulation. The narrative game group will be encouraged to use a mobile application that includes self-monitoring and feedback as well as a narrative-based active video game. The 15 calls for this group will emphasize concepts related to the game storyline. Counseling calls in both groups will occur weekly in months 1 - 3 and monthly in months 4 - 6. No counseling calls will occur after month 6, but both groups will be encouraged to continue using their apps. The primary outcome of the study is minutes of moderate to vigorous physical activity at six months. Other objectively measured outcomes include fitness and physical function. Self-reported outcomes include quality of life, depression, and motivation. This protocol will result in implementation and evaluation of two technology-based physical activity interventions among breast cancer survivors. Both interventions hold promise for broad dissemination. Understanding the potential benefit of adding narrative and game elements to interventions will provide critical information to interventionists, researchers, clinicians, and policymakers. This study is uniquely suited to investigate not just whether but how and why game elements may improve breast cancer survivors health. clinicaltrials.gov NCT02341235 (January 9, 2015).