Two hundred and ninety-five licensed floorball players from Finnish premier to fifth division were observed prospectively for one season to study the incidence, nature, causes and severity of floorball injuries. During the study period, 100 out of the 295 (34 %) players sustained 120 injuries. Thirty-seven percent (73/199) of the male players and 28 % (27/96) of the females suffered from an injury. The injury rate was 1.0 per 1000 practice hours for both sexes. The injury rates per 1000 game hours were 23.7 for men and 15.9 for women. One hundred injuries (83 %) were acute and the remaining 20 (17 %) were overuse injuries. Sprain was the most common type of injury in men while overuse injuries were the most frequent injury type in women. The lower extremity was involved in 62 %, spine or trunk in 19 % and upper extremity in 10 % of the injuries. The most commonly injured sites were the knee and ankle (22 % and 20 % of all injuries), followed by head and neck (8 %). In both sexes the majority of injuries were minor, level II, injuries. Ten of the knee injuries (38 %) were serious, level IV injuries, of which seven were ACL ruptures. In conclusion, the individual risk of injury in floorball is relatively low in game practice while rather high during the game itself. Before initiation of clinical trials on prevention of floorball injuries, an exact knowledge of the risk factors and mechanisms of floorball injuries are needed.