Background: In 2015, it has been estimated that 54,870 new cases of endometrial cancer will be diagnosed and about 10,170 women will die from it in United States. Previous studies suggested that high levels of coffee consumption may be associated with reduced risk of endometrial cancer among women ages 50-71. Although caffeine is a major ingredient of coffee, one study stated this inverse association does not differ according to caffeine content (regular coffee/decaffeinated coffee). However, the specific measurement of caffeine intake was not clear in that previous study. This study tries to investigate endometrial cancer risk in relation to caffeine intake and coffee consumption. Methods: The National Health and Nutrition Examination Survey (NHANES) 2003-2012 surveys were used in this study. A total of 5,847 postmenopausal women with valid cancer status were included in this study. Chi-square tests and t-tests were used to examine differences in proportions. Multiple logistic regression models were used to determine whether there was an association between the caffeine intake and endometrial cancer, after adjustment of various potential confounding variables. Weighting is supplied by NHANES data. Results: Among the women in the study, 1.37% of them were diagnosed with endometrial cancer. After multivariate adjustment, compared to women who did not have any caffeine intake, a significant increase in endometrial cancer was found in all levels of caffeine intake [OR = 25.646 (93 mg/day vs. non-taken), 95% CI: 2.210-135.434] and coffee consumption [OR = 42.865 (358 g/day vs. non-taken), 95% CI: 1.880-142.301]. The results also showed that black women and women using birth control pills were less likely to get endometrial cancer, but women who are excessively obese have a significantly higher risk of getting endometrial cancer. Conclusions: Our findings suggested that caffeine intake was associated with endometrial cancer. Compared to no caffeine intake, all level of coffee consumption and caffeine intake were risk factors of endometrial cancer. Black women had lower risk of endometrial cancer. A history of birth control pill use was a protected factor, while excess obesity was risk factor of endometrial cancer.