The purpose of the study was to test longitudinal (2 years across three occasions) associations between sport participation (SP) and self-esteem (SE) across adolescence (10–18 years), addressing the mediating role of perceived sport competence (PSC) from a developmental perspective. Three waves of data were collected from three age cohorts (10–12, 13–15, and 16–18 years) of school-aged youth (N = 1358). The results demonstrate that SP and SE are related across time and that PSC has an important mediating role in this relationship, both from a skill development and a self-enhancement perspective. In the skill development model, the mediating role of PSC was significantly stronger in the youngest cohort whereas the effect of PSC on subsequent SP in the self-enhancement model was significantly stronger in the 13–15 age group compared with the youngest age group.