Given the popularity of social media among young men who have sex with men (YMSM), and in light of YMSM’s elevated and increasing HIV rates, we tested the feasibility, acceptability and preliminary efficacy of a live chat intervention delivered on Facebook in reducing condomless anal sex and substance use within a group of high risk YMSM in a pre-post design with no control group. Participants (N = 41; 18–29 years old) completed up to eight one-hour motivational interviewing and cognitive behavioral skills-based online live chat intervention sessions, and reported on demographic, psychosocial, and behavioral characteristics at baseline and immediately post-intervention. Analyses indicated that participation in the intervention (n = 31) was associated with reductions of days of drug and alcohol use in the past month and instances of anal sex without a condom (including under the influence of substances), as well as increases in knowledge of HIV-related risks at 3-month follow-up. This pilot study argues for the potential of this social media-delivered intervention to reduce HIV risk among a most vulnerable group in the United States, in a manner that was highly acceptable to receive and feasible to execute. A future randomized controlled trial could generate an intervention blueprint for providers to support YMSM’s wellbeing by reaching them regardless of their geographical location, at a low cost.