In patients with endometrial cancer, obesity is associated with a well-differentiated histological grade but not with prolonged survival. It is possible that this lack of survival advantage is caused by incomplete surgical staging. In total, 716 patients with endometrial cancer were retrospectively reviewed. Obesity was defined as body mass index of ≥30 kg/m(2). The relationships between clinicopathological factors and disease-specific survival were analyzed by Cox regression analysis. Older age (hazard ratio, 1.6; 95% confidence interval, 1.1-2.4), advanced stage (hazard ratio, 11.2; 95% confidence interval, 7.2-17.5), high-risk histology (hazard ratio, 2.7; 95% confidence interval, 1.8-4.0), no hysterectomy (hazard ratio, 3.1; 95% confidence interval, 1.7-5.8) and no lymphadenectomy (hazard ratio, 2.0; 95% confidence interval, 1.3-3.0) were independently associated with poor disease-specific survival. Survival was similar in obese and non-obese women (hazard ratio, 0.9; 95% confidence interval, 0.5-1.6) despite the fact that obesity was significantly associated with younger age and a well-differentiated histological grade. Although there was no difference in the distribution of disease stage between the two groups, obesity was associated with lower rates of hysterectomy (3.6 vs. 6.1%, P = 0.23) and lymphadenectomy (25.0 vs. 36.4%, P = 0.017). Obese patients who underwent hysterectomy had a significantly better disease-specific survival than those who did not (P = 0.002). The 5-year disease-specific survival rate in obese patients who underwent lymphadenectomy was 6.2% better than that in those who did not 86.0 vs. 79.8%, P = 0.36 (not statistically significant). Poor-quality surgical staging in obese women may result in worse than expected survival outcomes.