Objectives: To develop and pilot test a mobile phone game intervention to decrease high risk sexual behavior (e.g. vaginal intercourse without condoms, multiple sexual partners, intercourse under the influence of drugs) in a group of 15-17 year-old Black and Latino adolescents. Methods: Iterative mixed methods design to create and develop a game prototype in waves of focus group discussion and play-testing with target audience. For pilot testing the game prototype, we collected data at baseline, after game play completion, and 8-weeks after completion in a pre-post design. Results: Pilot testing was completed by 26 predominantly Black and Latino adolescents aged 15-17. Most participants were male (61.5%), Hispanic (53.8%), and Black or multi-racial (73.1%). Pilot testing demonstrated evidence of impact with improvements in summary scores (Cronbach alpha 0.74-0.88) for sexual knowledge (p<0.0001), intentions regarding sexual decision making (e.g. intercourse under the influence of alcohol or drugs), risk perceptions (p=0.009), and self-efficacy regarding condom negotiation (p=0.003) from baseline to 8-week follow-up, demonstrating retention of impact. Although there was no measurable impact on summary intention scores, one individual question assessing intention to use effective contraception during future sexual encounters showed improvement (p=0.035). Conclusion: This successful pilot yielded important data about feasibility and preliminary impact of this game intervention, and provided information about next steps: adding more game content to further engage participants, targeting an older age group to maximize impact among sexually experienced adolescents, and focusing on an appropriate primary outcome for an R-type NIH grant, planned for October 2017.