Prevention of HIV transmission from patients living with HIV (PLH) is a high national priority and strategies that are easy to implement and sustain to eliminate sexual transmission acts among PLH are needed. We evaluated a brief intervention that focused primarily on the enhancing motivations and encouraging PLH to act in accordance with their values without providing the intensity of the existing evidence-based programs for PLH. Using a quasiexperimental design, six medical clinics in Los Angeles County, CA, were evaluated across three intervention conditions: 1) computerized delivery; 2) provider delivery; or 3) standard care. We examined longitudinal changes in patients' reports of the number of HIV-negative (HIV-) or serostatus-unknown sexual partners and the number of unprotected vaginal and anal sex acts. Among 566 PLH, PLH in the computerized delivery condition reported a significant decrease in the number of HIV-/unknown sexual partners compared with the provider delivery and standard care conditions and a significant decrease in the number of unprotected sex acts in comparison to the standard care condition. Computerized motivational interventions delivered in waiting rooms at medical clinics may be an efficient strategy to reduce unprotected sex acts among PLH.