BackgroundPhysical activity (PA) is a primary factor in reducing the risk of chronic diseases, yet only half of U.S. adults meet recommended levels.ObjectiveTo evaluate a PA self-monitoring pilot intervention using technology in obese adult primary care patients.MethodsThe project had a prospective, single group, pretest/posttest design using an accelerometer with a smartphone app. Obese adult primary care patients (N = 31) were followed over 6 months. Demographic (age, race, sex, marital status, educational level) and PA-relevant (PA, body mass index [BMI], self-efficacy for exercise [SEE]) data were collected at enrollment. PA and BMI were recorded monthly for 6 months. SEE was reassessed at 6 months.ResultsPA and BMI showed gradual improvement; however, changes in PA (p = .130), BMI (p = .326), and SEE (p = .877) at 6 months were not statistically significant. A strong, negative relationship was found between PA and BMI (r = −.727, p < .01). Anecdotal data indicated the smartphone app was acceptable to patients.ConclusionsData-supported clinician-initiated PA self-monitoring with a smartphone app was acceptable and showed favorable trends in improving PA and BMI in obese adult patients.Implications for NursingPrescribing PA self-monitoring using technology may be easily implemented.