People with lived or living experiences of drug use and services have been increasingly incorporated into nonpeer-led mainstream organizational settings as a unique workforce. Despite the much discussed effectiveness of peer services in achieving measurable outcomes, limited attention has been given to the experiential aspects of peer work from the perspectives of peers, clients, or others involved. This systematic review synthesized qualitative evidence examining the experiences of peer work in nonpeer-led drug use service settings. It focused on the benefits of incorporating peers as a unique workforce, the challenges they face, and the organizational factors that influence their practices. A search of 15 databases identified 3,940 unique citations, 33 of which met inclusion criteria. Thematic analysis was utilized to synthesize their findings. Foregrounding the uniqueness of peers' shared experience, studies have shown that incorporating peers into nonpeer-led settings can provide benefits at the client, organizational, and societal levels while promoting peers' personal and professional growth. The unique shared experience of peers can also present multidimensional challenges, such as triggering, boundary negotiation, and feelings of being trapped by their peer identity. To fully integrate peers into the system, organizations need to work with them to reconstruct organizational mission, culture, and structures in a way that recognizes and genuine commits to peers' unique values. This review highlights the significance of understanding peer uniqueness for organizations to create nourishing conditions for peer services and calls for future research exploring context- and setting-specific peer roles and organizational enablers and barriers.