Increased participation in sports has led to more sports injuries. Evidence-based methods to prevent sports injuries are needed. A systematic review was conducted of the effects of randomized controlled interventions to prevent sports injuries. A systematic search was performed of various databases and the reference lists of articles and reviews. Two reviewers independently extracted the data and assessed the methodological quality of the included trials. Thirty-two trials (24,931 participants) met the inclusion criteria. We found evidence of the preventive effect of 3 types of injury prevention interventions. In 5 trials including 6 different comparisons (2446 participants), custom-made or prefabricated insoles reduced lower limb injuries compared with no insoles in military recruits (risk reduction > or =50% in 4 comparisons). All 7 studies investigating external joint supports (10,300 participants) showed a tendency to prevent ankle, wrist, or knee injuries (risk reduction > or =50% in 5 studies). All 6 multi-intervention training programs (2809 participants) were effective in preventing sports injuries (risk reduction > or =50% in 5 studies). Various interventions may prevent sports injuries. A decreased risk of sports injuries was associated with the use of insoles, external joint supports, and multi-intervention training programs. More high-quality randomized controlled trials in different sports and populations are needed.