Substance use among HIV+ individuals can be a barrier to HIV care, resulting in poor health outcomes. Motivational interviewing (MI) is an effective intervention to reduce substance abuse and increase HIV-related health. Healthcare workers from various backgrounds can be effectively trained in delivering MI interventions; however, there has been limited evidence that peers can effectively deliver MI interventions with fidelity. Peers have traditionally worked in HIV care settings and represent a valid context for a peer-delivered intervention focused on motivational issues. We trained four peers in MI. In this paper, we describe the intervention, explain the MI training methods, and investigate whether peers can be trained in MI with fidelity. The MI training included didactic instruction, group workshops, and individual feedback sessions. Two of four peers achieved MI treatment fidelity as measured by the Motivational Interviewing Treatment Integrity Code Version 3.0. Overall, peers had difficulty using open-ended questions and querying pros and cons, skills thought necessary to elicit change talk. They also tended to give too much direct advice where reflections would have been appropriate. A challenge was training peers to change familiar ways of communicating. Nonetheless, they did well at assessing and highlighting motivation to change. The total training hours (40 h) was long compared with other published MI studies. However, the intervention included several components with two targeted change behaviors. It is likely that peers can be trained in MI with fidelity in less time given a more streamlined intervention. When working with peers who have life stressors similar to the target group, it is important to be flexible in the training.