BACKGROUND: Despite the fact that the recommendations of counteracting obesity advocate for changing lifestyle and physical activity habits, the prevalence of obesity continues to rise. The aim of the study was to investigate the effect of omega-3 PUFAs supplementation with lifestyle modification on anthropometric indices and Vo2max in overweight women. METHODS: Fifty overweight women aged between 20 to 45 years were recruited in this interventional study. Women randomly were divided into two experimental groups (n = 25). Group 1 received omega-3 supplement, aerobic exercise program, and a healthy diet education. Group 2 was similar to group 1, except in that patients received placebo instead of omega-3 capsules. Experimental and placebo group subjects were asked to take one supplementary capsule every day, for 8 weeks. Anthropometric indices were measured in the fourth and eighth weeks of the trial. The maximum aerobic capacity (Vo2max) was determined using a gas analysis device. The level of significance for comparing the results before and after the trial was considered at P < 0.05. RESULTS: According to the data, body weight, body fat percentage, waist circumference, and abdominal skinfold thickness significantly reduced in the omega-3 treated group compared to the control group during 8 weeks after the initiation of the study (P < 0.05). In addition, supplementation of omega-3, significantly improved the VO2max outcome compared to that of the control group (P = 0.03). CONCLUSION: According to the results, it seems that omega-3 PUFAS supplementation with lifestyle modification has positive effects on anthropometric indices and Vo2max in overweight women.