Swimmers’ competitive performance is a result of complicated interactions between physiological, biochemical, physical and psychological factors, all of which are strongly affected by water. Recently, great attention has been paid to the role of genetic factors such as the catechol-O-methyltransferase gene (COMT) influencing motivation, emotions, stress tolerance, self-control, sleep regulation, pain processing and perception, addictive behaviour and neurodegeneration, which may underlie differences in achieving remarkable results in sports competition. Thus, this study was performed to investigate the association between the COMT Val158Met (rs4680) polymorphism and athletic performance in Caucasian swimmers. A total of 225 swimmers (171 short distance (SDS) and 54 long distance swimmers (LDS)) of national or international competitive standard and 379 unrelated sedentary controls were genotyped using real-time polymerase chain reaction (real-time PCR). We found no significant differences in genotypic or allelic distributions between (1) male and female athletes; (2) SDS and LDS; (3) all athletes and sedentary controls (under codominant, dominant, recessive, and overdominant genetic models). No association was found between the COMT rs4680 polymorphism and elite swimming athlete status of the studied population. However, more replication studies are needed.