Endometrial cancer is a type of cancer that develops in the inner lining of the uterus, called the endometrium. After breast, lung, and colon cancer, endometrial cancer is the most prevalent malignancy of the female genital system in industrialized nations like North America and Europe. Phosphatase and Tensin homolog (PTEN), deleted on chromosome 10, is a tumor suppressor gene located on chromosome 10q23.31, which encodes a 403 amino acid protein with both lipid and protein phosphatase activities. One of the most common genetic abnormalities identified in human malignancies are somatic mutations in the PTEN gene. The tumor suppressor activity of the PTEN enzyme is reduced or completely lost as a result of PTEN gene mutations. Considering this information, it is thought that PTEN gene polymorphisms may be associated with the pathogenesis of the disease. The purpose of our study is to determine the relationship between functional PTEN polymorphisms IVS4 (–/+) and -9 C/G and endometrial cancer. DNAs belonging to 63 endometrial cancer patients and 63 control individuals were genotyped by PCR-RFLP method for 2 genetic variants of PTEN IVS4 (–/+) and -9 C/G gene. The expression level of PTEN protein was measured by the Elisa method from serum samples. Our results were evaluated with appropriate statistical methods. As a result of our study, no statistically significant difference was found in the risk of endometrial cancer and genotype frequencies of –9 C/G and IVS4 (-/+) variants (p> 0.05). It was detected that the serum level of PTEN lessened significantly in patients with endometrial cancer in comparison to the control (p <0.001). As a consequence, there was no evidence that the PTEN gene variations -9 C/G and IVS4 (-/+), whose efficacy we examined in our investigation, increased the incidence of endometrial cancer in the Turkish population. However, endometrial cancer patients were shown to have lower serum levels of the tumor suppressor protein PTEN.