Peer support is effective in improving self-management behaviors and health outcomes among individuals with Type 2 diabetes. Volunteer peer support programs offer a cost-effective resource for diabetes self-management support; however, factors affecting the retention of volunteer peer leaders remain understudied. Herein, we examined factors associated with volunteer retention and satisfaction among 34 predominantly Mexican-origin peer leaders who assisted patients from a Federally Qualified Health Center located on the US/Mexico border with their diabetes management. Peer leaders completed surveys with open- and close-ended questions at baseline, 6 months and 12 months. Quantitative and qualitative data analyses were guided by the Volunteer Process Model. Using nonparametric Mann-Whitney U tests, self-efficacy as a peer leader at 6 months was most associated with interest to continue volunteering (P = 0.01), and satisfaction with support from the program at 12 months was most associated with interest to continue volunteering (P = 0.01). The qualitative data indicated that the relationship between the peer leaders and their patients was the primary factor for a satisfying volunteer experience. Future research should focus on increasing peer leaders' self-efficacy and satisfaction with program support and examine how organizations can support the development of the patient--peer relationship. Practitioners should consider appealing to volunteer peers' motivations to promote their retention.