Our aim was to explore peer counselors' work and their role in supporting patients' adherence to antiretroviral treatment (ART) in resource-limited settings in Ethiopia and Uganda. Qualitative semi-structured interviews were conducted with 79 patients, 17 peer counselors, and 22 providers in ART facilities in urban and rural areas of Ethiopia and Uganda. Two main categories with related subcategories emerged from the analysis. The first main category, peer counselors as facilitators of adherence, describes how peer counselors played an important role by acting as role models, raising awareness, and being visible in the community. They were also recognized for being close to the patients while acting as a bridge to the health system. They provided patients with an opportunity to individually talk to someone who was also living with HIV, who had a positive and life-affirming attitude about their situation, and were willing to share personal stories of hope when educating and counseling their patients. The second main category, benefits and challenges of peer counseling, deals with how peer counselors found reward in helping others while at the same time acknowledging their limitations and need of support and remuneration. Their role and function were not clearly defined within the health system and they received negligible financial and organizational support. While peer counseling is acknowledged as an essential vehicle for treatment success in ART support in sub-Saharan Africa, a formal recognition and regulation of their role should be defined. The issue of strategies for disclosure to support adherence, while avoiding or reducing stigma, also requires specific attention. We argue that the development and implementation of support to peer counselors are crucial in existing and future ART programs, but more research is needed to further explore factors that are important to sustain and strengthen the work of peer counselors.