Objective To pilot test a two-session computer-delivered motivational intervention to facilitate adherence among youth with HIV newly prescribed antiretroviral treatment (ART). Methods Youth (N = 76) newly prescribed ART were recruited from 8 sites, and were randomized to the intervention or an active nutrition and physical activity control. Primary outcomes were HIV-1 viral load at baseline, 3 months, and 6 months, and self-reported adherence at 3 and 6 months. Results Satisfaction ratings were high. Effect sizes suggested that the intervention group showed a greater drop than controls in viral load from baseline to 6 months (Cohen’s d = 0.39 at 3 months; d = 0.19 at 6 months), and had greater percent undetectable by 6 months (d = 0.28). Effects sizes were medium to large for 7-day and weekend adherence. Conclusions A brief computer-delivered motivational intervention showed promise for youth starting ART and is ready to be tested in a full-scale clinical trial.