Background Mobile app-based interventions have been identified as potential facilitators for vaccination among young men who have sex with men (MSM). Objective This pilot study aimed to test the feasibility of a theoretically informed mobile health (mHealth) tool designed to reduce health disparities and facilitate human papillomavirus (HPV) vaccination among a sample of young MSM. Methods The development of the mHealth tool was guided by previous research, implementation intention theory, and design thinking. We recruited MSM aged 18-26 years through a popular online dating app and linked participants to our mHealth tool, which provided HPV vaccine information and fostered access to care. Results A total of 42 young MSM participated in this pilot study in Boston, Massachusetts. Participants reported variable HPV knowledge (ie, high knowledge of HPV risk factors and low knowledge of HPV-related cancer risks for men) and positive vaccine beliefs and attitudes. Of those who were either unvaccinated, not up to date, or did not report vaccine status, 23% (8/35) utilized the mHealth tool to obtain HPV vaccination. Participants primarily utilized the tool’s (1) educational components and (2) capabilities facilitating concrete vaccine action plans. Conclusions We recruited an underserved at-risk population of youth via an online dating app for our mHealth intervention that resulted in in-person health care delivery. This study was limited by enrollment challenges, including low willingness to download the mHealth tool to mobile devices.