SummaryThis research provides a systematic review of the literature on peer development groups (PDGs), a promising yet underexplored tool for individual and leadership development. Despite the growing interest in PDGs from both scholars and practitioners, the field remains fragmented, with inconsistent terminologies and limited theoretical grounding. This review seeks to clarify the core components, boundary conditions, inputs, processes, and outcomes of effective PDGs in professional settings, addressing the confusion and gaps in existing research. By adopting an adjudication approach, we provide a comprehensive synthesis of the evidence regarding the defining characteristics of PDGs and their impacts on individual development. We propose a new, scholarly definition of PDGs as organized small groups consisting of members of perceived similar status and roles who regularly meet to foster mutual growth by providing a supportive environment and a flexible agenda. We develop a conceptual framework that links key variables influencing PDG effectiveness and offers actionable insights for both researchers and practitioners. Our findings highlight opportunities for future research and suggest practical implications for implementing PDGs in organizational settings, ultimately contributing to a more cohesive and theoretically informed understanding of this valuable developmental practice.