Background: Young adulthood (18-29) is a critical time in the lifespan for the development of health behaviors. Wearable activity trackers are being adopted by young adults ahead of health promotion research. Methods: Semi-structured individual interviews were used to explore the experiences of young adult adopters of wearable activity trackers. Young adults (n=57) ages 18-29 were recruited using typical case and saturation sampling. College students (n=35) and straight-to-work (STW) young adults (n=22) were both interviewed. Interviews were recorded, transcribed, and analyzed using NVivo. Results: Most young adults reported little knowledge of the health benefits/risks associated with their health behavior, but high expectations as to how the wearable activity tracker would assist them in developing or maintaining a behavior. Self-regulatory aspects such as the self-monitoring, built-in goals, and feedback were seen as benefits. Many reported not setting goals independent of the device. Most reported increased self-efficacy as a result of their wearable activity tracker use, and viewed their device as positive non-judgmental support for their health behavior. Wearable activity trackers were also seen as valuable tools for impression management and allowed young adults to present more than one actual or aspirational social identity. Young adults reported that they signaled to the world that they were health conscious and active. Non-college educated young adults reported that wearable activity trackers portrayed them as modern and successful, while college students felt they appeared to others as techy and friendly. Conclusions: Wearable activity trackers have the potential to be an effective behavior change tool when used in conjunction with theory-based health promotion programming. Young adults are motivated to change or maintain health behaviors, but may need some additional support related to their health knowledge, expectations, and goal setting. In addition, the identities that young adults associate with wearable activity trackers are important as identity can influence health behavior. Future research should consider these identity related issues as they may play a key role in adoption and use of these health tools.