Current evidences suggest that nonsteroidal anti-inflammatory drugs can reduce the risk of several types of cancer, including breast, prostate, and colorectal cancer. However, evidences regarding the chemopreventive effect of aspirin to endometrial cancer are inconsistent. Therefore, we aimed to further explore the association. We searched PubMed, EMBASE, Web of Science, and Scopus to identify potentially eligible studies. After title/abstract screening and full-text review, we identified 7 cohort studies and 6 case-control studies. Data extraction and quality assessment were performed independently, and a random-effects model was used for data synthesis. Subgroup analysis was conducted based on obesity, hormone replacement therapy use, and cancer subtype; sensitivity analysis was conducted by pooling risk ratios of the highest dosage or longest duration of use. Dose-response relationship was assessed by a 2-stage linear dose-response model. Statistical heterogeneity was assessed by the I2 value and a χ2 test for the Cochrane Q statistic. In overall meta-analysis, the pooled risk ratio was 0.93 (95% confidence interval, 0.88–0.99), and no substantial statistical heterogeneity was observed (I2 = 0.0%, P = 0.550). In subgroup analysis, a negative association was observed for obese women and type I endometrial cancer. Higher dosage or frequency of aspirin use was significantly associated with a reduced risk, and long-term aspirin use was protective only for obese women. In conclusion, our study suggests that the use of aspirin can reduce the risk of endometrial cancer, particularly for obese women. However, the generalizability of our conclusion should be further studied for premenopausal women and type II endometrial cancer.