Although sport participation is encouraged throughout the lifespan, little research has been conducted on the role of sport in development later in life. This qualitative study explored adults' experiences of development within the context of Masters sport. We interviewed 14 adults (nine men and five women) aged 46-61 years involved in Masters sport. Data was interpreted drawing upon frameworks from youth sport (i.e., Personal Assets Framework for Sport; Côté, J., Bruner, M., Strachan, L., Erickson, K., & Fraser-Thomas, J. (2010). Athletes' development and coaching. In J. Lyle & C. Cushion (Eds.), Sport coaching: Professionalism and practice (pp. 63-83). Oxford, UK: Elsevier, Côté, J., Turnnidge, J., & Evans, M. B. (2014). The dynamic process of development through sport. Kinesiologia Slovenica, 20(3), 14-26, Côté, J., Turnnidge, J., & Vieerima, M. (2016). A personal assets approach to youth sport. In K. Green & A. Smith (Eds.), Routledge handbook of youth sport (pp. 243-255). New York, NY: Routledge; 4/5Cs of positive youth development; Lerner, R. M., Fisher, C. B., & Weinberg, R. A. (2000). Toward a science for and of the people: Promoting civil society through the application of developmental science. Child Development, 71(1), 11-20. doi:10.1111/1467-8624.00113; Vierimaa, M., Erickson, K., Côté, J., & Gilbert, W. (2012). Positive youth development: A measurement framework for sport. International Journal of Sports Science & Coaching, 7(3), 601-614. doi:10.1260/1747-9541.7.3.601), combined with past research on mid-life and older athletes. Six key themes emerged as contributing to adults' personal development through sport: competence and confidence, character, commitment, connection, cognition, and challenge. Masters sport contexts appeared to facilitate changes in assets (i.e., 6Cs) similar to those within youth sport, but assets often held different meanings within the context of later life. Applying frameworks from youth sport and developmental psychology to Masters sport contexts appears useful. The current findings support the modification of existing models and highlight their potential in identifying lifelong developmental outcomes of sport participation.