Interactive computer-based interventions (ICBI) are potentially scalable tools for use in real-world settings to promote sexual health and prevent sexually transmitted infections (STIs) and unintended pregnancies. We developed and assessed the feasibility and acceptability of an ICBI for promoting adolescent and young adult sexual health, and the effectiveness of the intervention in reducing unprotected sex, STIs, and unintended pregnancy.This pilot randomized controlled trial enrolled STI Clinic patients, in Seattle, Washington, who were 14-24 years old and reported unprotected vaginal sex during the last 2 months. Both the control and intervention group used a computerized survey to enter their sexual health and only the intervention group received the ICBI. The ICBI included personalized sexual health feedback from a physician avatar; instructive video modules advocating sexual health; and identification of one behavior to change. At 3-month follow-up, participants reported on interim sexual and pregnancy histories and underwent repeat STI testing. We assessed intervention impact on unprotected vaginal sex, number of sexual partners, incident STIs, and unintended pregnancy.Of 272 participants, 242 (89%) completed the study, of whom 65% were female. While these findings did not reach statistical significance, at 3-month follow-up, the intervention group reported a 33% lower rate of unprotected vaginal sex (no condom use) [IRR = 0.67, 95% CI: 0.44-1.02]; 29% fewer sex partners [IRR = 0.71, 95% CI: 0.50-1.03]; and 48% fewer STIs [IRR = 0.52, 95% CI: 0.25-1.08] when compared to the control group. Similarly, as compared to the control group, intervention females reported a lower rate of unprotected vaginal sex (no birth control) [IRR = 0.80, 95% CI: 0.47-1.35] and half as many unintended pregnancies (n = 5) versus control females (n = 10) [IRR = 0.51, 95% CI: 0.17-1.58]. In exploratory analyses, intervention females reported fewer partners [IRR = 0.71, 95% CI: 0.50-1.00] and a significantly lower rate of vaginal sex without condoms [IRR = 0.50, 95% CI: 0.30-0.85].The intervention was acceptable to both males and females, and at 3-month follow-up, there were non-significant reductions in risk behavior for all outcomes. Among females, exploratory analysis showed a significant reduction in vaginal sex without condoms.