When students learn with-and from-other students, it is called peer-assisted learning (PAL). How undergraduate medical students use their peers for their clinical-reasoning learning process remains unclear, although literature suggests that it is a promising learning strategy at this stage. This research therefore explores the question: 'How is PAL manifested in the clinical learning environment of undergraduate medical students with regard to developing clinical-reasoning skills?'. A constructivist paradigm with a sociocultural theoretical framework was adopted for this research, using PAL and workplace learning as theoretical background. Focused ethnography and a combination of template and open coding was used to gather and analyze qualitative data. Twenty semi-structured interviews were conducted with nine students, four residents, and seven clinical supervisors. A total number of 31.5 h were used for five clinical observations. Following categories were used to describe the data: (1) the role of PAL in the clinical-reasoning learning practice, in which PAL-theory was placed alongside clinical practice, (2) the role of different actors during PAL and (3) the PAL environment, in which contextual factors have been scrutinized. Students deploy various categories of PAL to advance their clinical-reasoning skills, although they were largely unaware of these processes, and facilitation of PAL is not consistently provided. Three topics of discussion are identified that need to be acknowledged: (1) the design of a PAL environment that is conducive to collaborative learning, (2) the shifting roles of peers when they enter clinical practice, and (3) the individualistic tendencies of students that can hamper PAL. Future research could focus on stimulating and facilitating PAL among the next generation of students and integrating PAL into the clinical practice workflow.