To examine the association between "overscheduling" and sports-related overuse and acute injuries in young athletes and to identify other potential contributing factors to create a working definition for "overscheduling injury." Survey. Six university-based sports medicine clinics in North America. Athletes aged 6 to 18 years (13.8 ± 2.6) and their parents and pediatric sports medicine-trained physicians. Questionnaires developed from literature review and expert consensus to investigate overscheduling and sports-related injuries were completed over a 3-month period. Physician's clinical diagnosis and injury categorization: acute not fatigue related (AI), overuse not fatigue related (OI), acute fatigue related (AFI), or overuse fatigue related (OFI). Overall, 360 questionnaires were completed (84% response rate). Overuse not fatigue-related injuries were encountered most often (44.7%), compared with AI (41.9%) and OFI (9.7%). Number of practices within 48 hours before injury was higher (1.7 ± 1.5) for athletes with OI versus those with AI (1.3 ± 1.4; P = 0.025). Athlete or parent perception of excessive play/training without adequate rest in the days before the injury was related to overuse (P = 0.016) and fatigue-related injuries (P = 0.010). Fatigue-related injuries were related to sleeping ≤6 hours the night before the injury (P = 0.028). When scheduling youth sporting events, potential activity volume and intensity over any 48-hour period, recovery time between all training and competition bouts, and potential between-day sleep time (≥ 7 hours) should be considered to optimize safety. An overscheduling injury can be defined as an injury related to excessive planned physical activity without adequate time for rest and recovery, including between training sessions/competitions and consecutive days.