Aims. Previous evidence has proved that interleukin-31 (IL-31) and interleukin-33 (IL-33) can be potential markers in some cancers' formulation. We aimed to determine the potential role of IL-31 and IL-33 in prognosis of endometrial cancer patients. Methods. Serum samples were collected from 160 patients with endometrial cancer and 160 healthy controls. The ELISA kits (Raybio® Systems) specific for human IL-31 and human IL-33 were used. Serum levels of tumor markers (CEA, CA-125, and CA19-9) were measured by chemiluminescence immunoassay. A two-side P value < 0.05 was indicated to be significant. Results. Serum levels of IL-31 and IL-33 in patients were significantly elevated compared to those of healthy controls. The interleukin levels were also related to clinical characteristics, including tumor stages, depth of invasion, and existence of node metastases and distant metastases. The sensitivity and specificity of IL-31 and IL-33 were higher than the counterparts of tumor markers, both separately and in combination of IL-31, IL-33, and the clinical markers. Conclusions. This report is the first one mentioning the possible association between serum IL-31 and IL-33 and endometrial cancer. With their sensitivity and specificity, the interleukins may be useful biomarkers for endometrial cancer's prognosis.