Our study team developed the MyPEEPS Mobile App for improving HIV prevention behaviors in diverse young men. We conducted a randomized controlled trial and evaluated the preliminary outcomes in the first half (N=350) of our intended study sample. Higher self-efficacy for HIV prevention behaviors (p=0.0042) and more recent HIV tests in the past 3 months (p=0.0156) were reported by the intervention group compared to control. Numbers of condomless anal sex acts were lower among the intervention group for both insertive anal sex acts (p=0.0283) and receptive anal sex acts (p=0.0001). Preliminary results indicate that some sexual risk behaviors were reduced among the intervention group in the preliminary analytic sample.