Background: The popularity of team sports is growing among young people. High training volume and intensity may predispose young athletes to overuse injuries. Research to date has tended to focus on acute injuries rather than overuse injuries. The purpose of this study was to examine the occurrence, nature, and severity of overuse injuries in youth basketball and floorball, with the hypothesis that overuse injuries are frequent in youth team sports. Methods: The study comprised a total of 401 Finnish team sports athletes (207 basketball and 194 floorball players). The data were collected using a detailed questionnaire. The participants (mean age 15.8±1.9 years) responded to the questionnaire covering information on overuse injuries during the previous 12 months. Results: A total of 190 overuse injuries was reported (97 in basketball and 93 in floorball). In both sports, most of the injuries involved the lower extremities (66% and 55% of all injuries in basketball and floorball, respectively). In basketball, the most commonly injured site was the knee (44 cases, 45%). In floorball, the most commonly injured sites were the lower back/pelvis (36 cases, 39%) and knee (32 cases, 34%). Overuse injuries caused an average time loss from full participation of 26±50 (median 7) days in basketball and 16±37 (median 5) days in floorball. Conclusion: Overuse injuries are a common problem in youth team sports, and often cause long-term absence from full participation. The findings suggest that injury reduction and training load monitoring strategies are needed in the field. More research using explicit prospective data collection is needed to better understand the problem.