Background: In the United States, young men who have sex with men (YMSM) remain disproportionately affected by human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs). Although routine HIV/STI screening is pivotal to the timely diagnosis of HIV and STIs, initiation of appropriate treatment, and reduced onward disease transmission, repeat screening is underused. Novel interventions that incorporate elements of games, an approach known as gamification, have the potential to increase routinization of HIV/STI screening among YMSM., Objective: The study aims to test the hypothesis that an incentive-based intervention that incorporates elements of gamification can increase routine HIV/STI screening among YMSM in California., Methods: The study consists of a formative research phase to develop the intervention and an implementation phase where the intervention is piloted in a controlled research setting. In the formative research phase, we use an iterative development process to design the intervention, including gathering information about the feasibility, acceptability, and expected effectiveness of potential game elements (eg, points, leaderboards, rewards). These activities include staff interviews, focus group discussions with members of the target population, and team meetings to strategize and develop the intervention. The final intervention is called Stick To It and consists of 3 components: (1) online enrollment, (2) Web-based activities consisting primarily of quizzes and a countdown "timer" to facilitate screening reminders, and (3) in-person activities that occur at 2 sexual health clinics. Participants earn points through the Web-based activities that are then redeemed for chances to win various prizes during clinic visits. The pilot study is a quasi-experimental study with a minimum of 60 intervention group participants recruited at the clinics, at community-based events, and online. We will compare outcomes in the intervention group with a historical control group consisting of individuals meeting the inclusion criteria who attended study clinics in the 12 months prior to intervention implementation. Eligible participants in the pilot study (1) are 18 to 26 years old, (2) were born or identify as male, 3) report male sexual partners, and 4) have a zip code of residence within defined areas in the vicinity of 1 of the 2 implementation sites. The primary outcome is repeat HIV/STI screening within 6 months., Results: This is an ongoing research study with initial results expected in the fourth quarter of 2017., Conclusions: We will develop and pilot test a gamification intervention to encourage YMSM to be regularly screened for HIV/STIs. The results from this research will provide preliminary evidence about the potential effectiveness of using gamification to amplify health-related behavioral change interventions. Further, the research aims to determine the processes that are essential to developing and implementing future health-related gamification interventions., Trial Registration: Clinicaltrials.gov NCT02946164; https://clinicaltrials.gov/ct2/show/NCT02946164 (Archived by WebCite at http://www.webcitation.org/6ri3G4HwD)., (©Christopher M Mejia, Daniel Acland, Raluca Buzdugan, Reva Grimball, Lauren Natoli, Mark R McGrath, Jeffrey D Klausner, Sandra I McCoy. Originally published in JMIR Research Protocols (http://www.researchprotocols.org), 17.07.2017.)