The relative age effect (RAE) suggests that athletes may be provided with greater opportunities for success depending on the position of their birthdate in a sport's selection year. While the effect has been well established in men's sports, less is known about women's sports. This study examined the RAE in developmental girls' hockey in Ontario. Relative age, player position, age division, and level of play were provided by the Ontario Women's Hockey Association for 36,555 registrants. Older players were over-represented, and younger players under-represented across all age divisions and levels of play. This suggests that the RAE is present in developmental girls' hockey, the magnitude of which varies with level of play and player position.