Sex Positive! is a two-arm, video-based web intervention aimed at reducing condomless anal sex (CAS) with partners of known and unknown serostatus that was delivered online to a racially and ethnically diverse sample of 830 gay, bisexual, and other men who have sex with men living with HIV. Men in each arm received 6 weekly videos after completing a baseline assessment and 4 weekly booster videos following a 6-month assessment. Follow-up assessments were conducted every 3 months for 1 year. At 3-month follow-up, men in the intervention arm reported significantly reduced risk of having unknown serodiscordant CAS partners than men in the control arm (RR 0.60, 95% CI 0.39-0.92), partially supporting study hypotheses. Aside from this finding, similar reductions in sexual risk behaviors were observed in both arms over the study period. There is much to be learned about video-based web interventions in terms of methodological development and intervention delivery, including frequency and duration of intervention components.