There is growing recognition that transformational leadership (TL) theory may hold significant potential for coaching research in youth sport (Arthur, Woodman, Hardy, Ong, & Ntoumanis, 2011). Evidence suggests that coaches’ use of TL behaviours can be linked with positive athlete outcomes, such as motivation, performance, and personal development (Charbonneau, Barling, & Kelloway, 2001; Vella, Oades, & Crowe, 2013). While the existing literature offers valuable insight into the types of athlete outcomes that may be associated with TL, studies evaluating how these outcomes can be acquired in sport are limited. In order to illustrate how TL theory can be employed as an effective framework for exploring the relationships between coaches’ behaviours and positive youth development in sport, it is crucial to gain a better understanding of how TL exerts its influence on athlete outcomes. Thus, the purpose of the present study was to synthesize and integrate the research that has examined the processes by which TL influences followers’ psycho-social development in various disciplines. A systematic search was conducted of six electronic databases covering a wide range of disciplines, including business, health, education, and sport and exercise psychology. Peer-reviewed, original studies that were published in English were included in this review. The initial search yielded 2077 papers, of which 192 met the selection criteria and were retained for analysis. A descriptive, content analysis-based approach was used to assess emerging patterns in research design and study findings. Results revealed numerous processes, at the individual, interpersonal, and environmental levels, that contribute to the relationships between TL and follower development. Study samples mainly consisted of adults from organizational settings. All of the included studies employed a quantitative, questionnaire-based methodology, and the majority of papers were cross-sectional in nature. A conceptual model is proposed, along with recommendations for future coaching research in youth sport.