We investigated the effect of moderate and vigorous aerobic exercise (MAE and VAE) on serum oxidized low-density lipoprotein (ox-LDL) levels and total antioxidant capacity (TAC) in voluntary and untrained healthy subjects. All subjects were randomly divided into three groups, including VAE (80–85% of maximal reserve heart rate) (n = 15), MAE (60–65% of maximal reserve heart rate) (n = 17), and control (n = 12). Exercise groups exercised in three sessions per week for 8 weeks. MAE and VAE did not significantly alter serum ox-LDL, total cholesterol (TC) and TAC (p > 0.05), while serum high-density lipoprotein (HDL-C) and HDL-C/TC ratio were significantly increased (p < 0.05). In the exercise groups, maximal oxygen uptake (V_O2max) was higher and body mass index (BMI) was lower than control group (p < 0.05). There was a significant positive correlation between baseline V_O2max and TAC and HDL-C. TAC had a significant negative correlation with TC, LDL-C and BMI. We conclude that serum ox-LDL and TAC were not affected by exercise, however, a positive correlation between V_O2max and TAC and a negative correlation between TAC and LDL-C as well as TC suggest a correlation between physical training and an improved antioxidant defense system.