The purpose of this study was to examine age and gender differences in the quality of sport friendship, assess the relationship between friendship quality and motivation related variables, and obtain additional support for the validity of the Sport Friendship Quality Scale (SFQS; Weiss & Smith, 1999). Tennis players (N = 191, ages 10-18 years) completed the SFQS and other measures salient to the questions of the study. A MANOVA revealed that adolescent athletes ages 14-18 years rated loyalty and intimacy, things in common, and conflict higher than did younger players, ages 10-13 years, who in turn rated companionship and pleasant play higher. Girls rated self-esteem enhancement and supportiveness, loyalty and intimacy, and things in common higher than did boys, who rated conflict higher. Regression analysis indicated that companionship and pleasant play, conflict resolution, and things in common predicted higher tennis enjoyment and commitment. The collective findings - confirmation of the SFQS six-factor structure, relationships between sport friendship quality dimensions and peer acceptance, and relationships of sport friendship quality dimensions with Harter's (1988) close friendship measure - support the validity of the SFQS.