Objective: Diagnosis of endometrial cancer (EC) is made by biopsy sampling with pathological analysis, but it is extremely important to make an accurate diagnosis in order to plan the specific treatment. We hypothesized that human epididymis protein 4 (HE4) in endometrial tissue and in serum could be beneficial for a more precise diagnosis. Material and Methods: This prospective study compared patients with EC against non- EC, matched through several variables. The inclusion criteria were: females older than 18 years who accepted to participate; who had never undergone surgery for other oncological pathologies (ovarian, colon, cervical carcinoma or uterine sarcoma); none of them had received preoperative chemo- or radio-therapy; and no participant had any severe renal or liver pathology. All had pre-surgery blood sampling and then underwent hysterectomy. Histopathological assessment of endometrial samples was made by a pathologist who compared normal histopathological staining with HE4-antibody staining. Results: In total there were 34 cases and 35 controls recruited. There was poor correlation between tissue HE4 in patients with and without carcinoma. However, serum HE4 was significant for the diagnosis of endometrial carcinoma (median EC: 123.1 U, median NE: 64.67 U, p=0.002), although the carbohydrate antigen 125 level was not significant (p=0.208). Conclusion: The findings concerning the utility of HE4 contrast with earlier reports. However, the conclusions for serum measurements are positive and suggest that the tumor marker HE4 seems to be able to diagnose EC. (J Turk Ger Gynecol Assoc 2021; 22: 161-7)