Abstract Water sport is one of the popular categories of all the field of sports. Without proper warm-up the risk of injuries is a real danger during the trainings and matches. Self-Myofascial Release (SMR) is a technique used to treat myofascial restrictions and also restore soft-tissue capability. The equipment which is used in Self-Myofascial Release is a foam roller. Foam rolling is thought to improve muscular function, performance, overuse, and joint range of motion. Since musculoskeletal injuries in water polo players have proved in many studies and self-myofascial release is an important technique in reducing injuries, we decided to investigate the mentioned issue in our research. The investigation was carried out in the Debrecen City water polo team with 5 participants. The age of the 5 participants was 17.2±0.45 years in average (±SD); their height was 182.2±6.3cm, and their weight was 78.4±5.6kg (mean±SD). Only 2 of them had previous knowledge about the SMR technique. The all-sit test, the stork position test and the sit and reach test were performed to investigate the effect of the SMR technique on the flexibility of the muscles and other soft tissues. The players made warm-up without SMR technique in the unpaired weeks and with the SMR technique in the paired weeks. The results showed remarkable changes in the duration of keeping the wall-sit and stork positions as well as in the distance in the sit and reach test. The relative change in the duration of keeping the wall-sit position at the end of the 6th week was 151±33.4% (p<0.02). There was an increase in the duration of stork position on the right foot (173.3± 93.6%; mean±SD; n=5, p<0.03). The time while keeping the stork position on the left foot was almost doubled by using the SMR technique at 4th week (197.4± 21.4%; mean±SD). The change in the result of the sit and reach test is equal to 230±34.6% even in the 4th week. All of the participants answered that the SMR technique increased the flexibility and range of motion of their joints, and decreased the muscle rigidity. They felt that the new method made them more appropriately prepared for training and matches. 4 of them would use this technique in the future. We concluded that the SMR technique is a useful tool in prevention of the sports injury, easy to perform and seems to be very effective. Further studies are necessary to check the long-lasting effect of the regulars use.