The present study examined perceived sport competence and affect experienced in sport as possible determinants of children's levels of self- esteem. The sample consisted of 183 summer sport program participants ranging in age from 8 to 13 years. The children completed self-report questionnaires that assessed the constructs of interest. Hypothesized relationships among the constructs were then examined using structural equation modeling techniques. The results revealed that both structural models tested provided an adequate fit with the sample data. For the affect mediator model, perceived competence significantly influenced positive affect and to a lesser degree negative affect, while only positive affect influenced self-esteem. For the perceived competence mediator model, only positive affect significantly influenced perceived competence, which in turn significantly influenced self-esteem. Thus, higher scores on perceived competence and positive affect were associated with higher scores in children's self- esteem.