Chronic inflammation may be important in endometrial cancer etiology. Several established endometrial cancer risk factors, particularly obesity, are hypothesized to operate through this pathway by increasing proinflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), and acute-phase protein C-reactive protein (CRP). This study sought to investigate the association between inflammatory markers and the risk of endometrial cancer (types I and II). We recruited 519 incident endometrial cancer cases and 964 frequency age-matched controls in this population-based case–control study in Alberta (Canada) from 2002 to 2006. Participants completed in-person interviews, were assessed for anthropometric measures, and provided 8-h fasting blood samples either preoperatively or postoperatively. Blood was analyzed for the concentrations of TNF-α, IL-6, and CRP by immunoassay. Endometrial cancer cases had consistently higher mean levels of TNF-α, IL-6, and CRP compared with controls in these predominantly postmenopausal women. After adjusting for age, all markers were associated with statistically significant increased risks for endometrial cancer; however, after multivariable adjustment, only the risk from CRP remained elevated (odds ratio=1.22, 95% confidence interval: 1.02–1.47). Similarly, upon stratification by cancer type, only CRP was associated positively with an increased risk for type I endometrial cancer (odds ratio=1.25, 95% confidence interval: 1.03–1.52). All markers were associated with an elevated risk for the more rare and aggressive type II cancers; however, these findings were statistically nonsignificant, likely because of the small number of cases in this group. In conclusion, we found epidemiologic evidence for an association between CRP and the risk of endometrial cancer, which was slightly stronger for type I cancer. No associations emerged for TNF-α and IL-6.