Background: Cancer survivors have high rates of sedentary behavior leading to obesity and cardiovascular disease. Physical activity improves quality of life (QOL) and reduces morbidity and mortality. However, cancer survivors commonly cite motivation as a barrier to increasing physical activity. We hypothesized that a motivational text-messaging feedback system linked to a Fitbit Flex activity tracker would increase the activity level of survivors and those undergoing cancer treatment. Methods: 29 participants were enrolled in an IRB-approved single-institution study. Eligibility allowed any cancer/stage, ≤2 days of exercise per week, life expectancy of 12+ months, and smartphone access. After baseline fitness/QOL testing, participants were provided a Fitbit Flex activity tracker. A text-messaging program automatically uploaded data from the tracker via an application programming interface and provided personalized text message feedback to subject’s smartphone daily for 3 months. Primary endpoint was change in step count from baseline to 3 months, with additional endpoints of change in 6 minute walk/QOL measures at 3 months, and continued exercise/use of tracker at 6 months. Results: To date, 24 have completed the 3 month program. Both academic and community sites participated, including areas with limited internet access. Most participants were female (71%) and white (63%). Eight cancer types and all stages were represented. Three participants withdrew – one because of lost tracker, one cancer death, and one “disappointed” with tracker function. Median daily steps at baseline were 3773 (IQR 2928) and 4365 at 3 months (IQR 4864). 42% had at least a 20% increase in median step count at 3 months. Improvement was noted in 45% of survivors and 38% of active treatment participants. Participants frequently used research nurses for guidance on use of wearable tracker (e.g. syncing, charging, features). Conclusions: Activity tracker with personalized daily feedback via text message successfully motivates cancer patients to increase daily activity. Patients are interested in health technology, but require technical support and coaching to maintain use. Clinical trial information: NCT02627079