AimTo identify strategies that develop clinical nursing leadership competencies among staff nurses, and to explain the contextual elements and mechanisms that underpin the development of clinical nursing leadership competencies.DesignRealist review according to the Realist and Meta‐narrative Evidence Syntheses—Evolving Standards (RAMESES).Data SourcesPubMed, Embase, CINAHL, Web of Science, Wiley Online Library, PsycInfo and ProQuest were searched from January 2000 until October 2022.Review MethodsThree iterative phases: (1) development of initial programme theory, (2) structured searches for relevant published and grey literature and (3) data synthesis and interpretation by researchers and theory triangulation, and discussions within the research group.ResultsMultiple context–mechanism–outcome configurations were extracted from 10 reports that explain how, under what circumstances and why strategies can facilitate (or discourage) staff nurses to act as clinical leaders. Reports were both quantitative and qualitative in design, originating from English‐speaking countries only.ConclusionsA logic model was developed and suggests four contexts and five mechanisms underlying the development of clinical nursing leadership. Growth in clinical nursing leadership was mainly experienced through experiential learning, which was enhanced by a supportive relationship with a coach or mentor, the use of reflective practices and modelling from other leaders. Furthermore, a supportive work environment triggers ownership, confidence and motivation, and thereby growth in clinical nursing leadership competencies.ImpactFostering competencies for clinical leadership among staff nurses requires multifaceted strategies. Strategies are successful if, and only if, they combine learning by doing, by knowing and by observing, and establish a responsive work environment. Hospital policy should ensure that staff nurses have access to reciprocal relationships with role models or a coach. In order to grow as clinical nurse leader, ownership and self‐reflection on own leadership behaviour need to be facilitated.No Patient or Public ContributionProspero ID CRD42021292290.