Using a sample of student-athletes’ (N=64) first year (seventh grade) enrolled at a school with a sport profile, the aim of this longitudinal study was to investigate (a) levels and changes as regards to worry about sport performance, perception of peer climate, and perceived competence; and (b) the relationship in levels and changes between these studied variables. The primary results from latent growth models (LGMs) and parallel process LGMs revealed that, during their first year, the student-athletes’ level of worry and perceived ego-oriented peer climate increased, whereas perceived competence decreased. Further, the results showed that perceived competence was negatively associated with worry at the beginning of the students’ first year. The slope of perceived ego-oriented peer climate was positively associated with the slope of worry. Future research in relation to the findings is discussed, and recommendations for future actions are given.