Introduction: Few health-promoting mobile applications (apps) have automated feedback text messages for individual behavioral outcomes achieved with self-monitoring of multiple lifestyle behaviors. One such app is “My HeartHELP” that was developed for general adult population to promote heart-healthy lifestyle behaviors. This app targets six heart-healthy lifestyle behaviors, such as physical activity, non-sedentary behaviors, healthy eating behaviors, non-smoking, no alcohol binge drinking, and self-assessment of body weight. It was designed with three essential technologies: 1) text messaging the users for information on cardiovascular health, 2) self-monitoring of six lifestyle behaviors, and 3) automated and personalized feedback text messaging to users for behavioral outcomes obtained from self-monitoring. Objective: We aimed to evaluate the feasibility and acceptability of the “My HeartHELP” app. Methods: The participants were 30 community residents, who had at least one criterion of metabolic syndrome. To evaluate the feasibility, we assessed the completion of participants’ self-monitoring of their lifestyle behaviors by requesting them to use the app every day for four weeks. To evaluate the acceptability, we assessed behavioral changes and satisfaction of the participants using self-administered questionnaires before and after four weeks of using the app, and by conducting one session of a focus group interview after four weeks. Results: The mean age of participants was 41.1 years. During four weeks, they accessed the app on average 1.8 times per day, and 95% of the participants adhered to more than 75% of “completion of daily self-monitoring of each lifestyle behavior.” These data met the criterion of more than 70% of the participants who adhered. Participants reported improved behavioral changes in moderate-intensity physical activity (p = .020), non-sedentary behavior (p = .003), fruit and vegetable intakes (p = .001), no sugar-sweetened beverage intake (p = .005), and less fast-food intake (p = .018). On a five-point Likert scale, participants reported the following mean scores, i.e., 4.0 for easiness, 3.6 for health benefits, 3.9 for convenience, and 3.8 for recommendation to others. Data obtained from the focus group interview reflected that automated and personalized feedback text messages motivated the participants to promote their healthy lifestyles, and they suggested modifying the app interface for entering food intakes. Conclusions: The study results showed that “My HeartHELP” is a feasible and acceptable mobile app to promote self-monitoring and motivation for heart-healthy lifestyle behaviors.