This study has been conducted to determine whether mean values of peak oxygen consumption (VO2peak), anaerobic test parameters and knee isokinetic test measurements are different among guanine nucleotide-binding protein, beta-3 (GNB3) genotype groups in a group of basketball players. Methods: Seventy-two healthy male (mean age, 22.9 +/- 5.3 years) basketball players from the first division of national league participated. We studied GNB3 gene c. 825C>T (rs5443) polymorphism, then divided the subjects into three groups as CC (n = 21), CT (n = 35), and TT (n = 16). Mean VO2peak, Wingate anaerobic test results, and isokinetic knee muscle strength measurements were compared among the genotype groups. Results: Mean VO2peak (60.1 +/- 3.9; 56.7 +/- 3.6; and 57.8 +/- 3.3, respectively, p < 0.01), mean anaerobic minimum power (5.1 +/- 0.4; 5.3 +/- 0.5; and 4.4 +/- 0.5 W/kg, respectively, p < 0.001), mean anaerobic power drop (57.0 +/- 6.2; 54.2 +/- 6.9; and 62.9 +/- 5.3%, respectively, p < 0.001) were significantly different among the study groups, CC, CT, and TT. Individuals with TT genotype exerted lower performance in terms of isokinetic knee muscle strength. Conclusion: The presence of 825T-allele may impair athletic performance and may serve as a genetic marker of low capacity for athletic performance in male basketball players.