Homeless people are increasingly supported by peer workers in one-on-one mentorship relations called intentional unidirectional peer support (IUPS). Insight is therefore needed into the application and outcome of IUPS for this vulnerable population. This study examined the outcomes, critical elements, and working mechanisms of IUPS within homeless services from the perspective of both clients receiving IUPS and peer workers providing IUPS. Semi-structured face-to-face interviews were held with ten homeless clients and ten peer workers. According to participants, IUPS enhances clients’ self-image, advances their personal growth, and results in better engagement with needed services. Rapport and empathy, a trustworthy and empowering relationship, as well as support, guidance, and mediation are what makes IUPS work according to the participants. The inclusion of both perspectives has led to a deeper understanding of what makes IUPS work for homeless people. Implications for practice are discussed.