Youth living with HIV (YLH) are at particularly high risk for poor retention in HIV primary care. This study utilized Motivational Interviewing (MI) to improve youth retention in primary care and compared the fidelity and outcomes of peer outreach workers (POW) to masters level staff (MLS). Eighty-seven YLH were randomized to receive two MI sessions from POW or MLS. YLH were aged 16-29 and 92% were African American. Thirty-seven audiotaped sessions were coded with the Motivational Interviewing Treatment Integrity (MITI) coding system. Retention in care was assessed by review of medical records. POW had higher fidelity on two MITI scales, and did not differ from MLS on remaining three scales. While both groups improved the regularity of primary care appointments, the effect size for POW on retention in care and intervention dose was larger than that of MLS. The results suggest that POW can provide MI with quality comparable to MLS with adequate training and supervision. MI provided by POW to improve retention in health care services may increase the cost-effectiveness of evidence-based practices in urban settings.