Irisin is a myokine/adipokine with potential role in obesity and diabetes. The purpose of the present study was to assess irisin levels and its association with insulin resistance and oxidative stress markers in premenopausal normal-weight and obese women. Ten obese (mean body mass index, 32.65±3.04 kg m−2) and 10 normal-weight (23.00±2.23 kg m−2) premenopausal women were involved in the present study. Anthropometric, and body composition parameters, blood chemistry, oxidative stress markers, and irisin concentrations of different groups were measured. Correlation analyses were performed between irisin and other measured parameters. Plasma irisin levels were lower in the obese group than the normal-weight group (p<0.05). Glucose, homeostasis model assessment index (HOMA-IR), and MDA levels in the obese group were higher than that in the normal-weight group (p<0.05). Plasma irisin was negatively correlated with insulin (r=−0.648, p<0.05), HOMA-IR (r=−0.664, p<0.05) and MDA (r=−0.690, p<0.05). These data suggest that irisin levels are decreased with obesity, and irisin may have an antidiabetic and antioxidant effects.