Although peer interventionists have been successful in medication treatment-adherence interventions, their role in complex behavior-change approaches to promote entry and reentry into HIV care requires further investigation. The current study sought to describe and test the feasibility of a standardized peer-mentor training program used for MAPPS (Mentor Approach for Promoting Patient Self-Care), a study designed to increase engagement and attendance at HIV outpatient visits among high-risk HIV inpatients using HIV-positive peer interventionists to deliver a comprehensive behavioral change intervention. Development of MAPPS and its corresponding training program included collaborations with mentors from a standing outpatient mentor program. The final training program included (1) a half-day workshop; (2) practice role-plays; and (3) formal, standardized patient role-plays, using trained actors with "real-time" video observation (and ratings from trainers). Mentor training occurred over a 6-week period and required demonstration of adherence and skill, as rated by MAPPS trainers. Although time intensive, ultimate certification of mentors suggested the program was both feasible and effective. Survey data indicated mentors thought highly of the training program, while objective rating data from trainers indicated mentors were able to understand and display standards associated with intervention fidelity. Data from the MAPPS training program provide preliminary evidence that peer mentors can be trained to levels necessary to ensure intervention fidelity, even within moderately complex behavioral-change interventions. Although additional research is needed due to limitations of the current study (e.g., limited generalizability due to sample size and limited breadth of clinical training opportunities), data from the current trial suggest that training programs such as MAPPS appear both feasible and effective.