Core strength is defined as producing or protecting the strength, and putting against a resistance. Exercise can cause free radical formation according to its intensity and duration which increase metabolic processes and oxygen consumption. Oxidative stress, muscle fatigue, muscle damage and its pain because of this increase are related with decreasing physical performance. Purpose of this study was to investigate effects of core training on antioxidant system. Participants of this study were 13 basketball players who accepted to attend voluntarily. Mean heights of participants were 175.73±4.26 and mean weights of them were 63.61±5.48. Group followed 8 weeks core training three times a week and 2 hours for each time. Venous blood samples were taken from participants at the end of first, fourth and eighth week trainings. Samples were analyzed according to Antioxidant (Superoxide Dismutase (SOD), Glutatyon Peroksidaz (Gsh-Px), Catalase (CAT) and Malondialdehyde (MDA) parameters. Data were analyzed with Multivariate ANOVA and bonferroni follow-up tests. Results showed that second and third SOD values were significantly higher than first test SOD value before core training process (F(2)= 7.08, p<0.05). Even increase happened, there were not statistically significant difference on GSH (F[subscript (2)]= 2.57, p>0.05) and CAT (F[subscript (2)]= 2.80, p>0.05) values. Moreover, second and third MDA values statistically significant decreased according to MDA first test value (F[subscript (2)]= 7.43, p<0.05). As a conclusion, core exercises increased oxygen consumption which causes free radical formation. It was determined that detrimental effects of this free radical formation were repressed by increasing SOD activity value and it decreased MDA which is free radical parameters. It is thought that increasing antioxidant level via exercise can effect athletes' performances positively