Background and objectives: Cyclooxygenase-2 functions as an enzyme which synthesize prostaglandins from Arachidonic acid Cyclooxygenase -2 is one of the important factors in maintaining the endometrium during menstrual cycle. The Aim of this study was to assess expression of Cyclooxygenase-2 in endometrioid carcinoma by immunohistochemistry to explore association between Cyclooxygenase-2 expression and a certain number of clinicopathologic variables. Methods: A retrospective study was carried out for seventy-eight blocks that were preseved in formalin and embedded in paraffin of endometrioid carcinoma were obtained and randomly selected from a private laboratory in Erbil city during October 2020 to October 2022. COX-2 rabbit monoclonal antibody was used to satin slides obtained from endometrioid carcinoma blocks and the expression was scored by multiplying the number of stained cells by the intensity of staining. Results: Cyclooxygenase-2 expressed in 15.4% of cases of study cases. It is down-expressed in high grade endometrioid carcinoma while over-expressed in cases with myometrial invasion ?50%. Regarding other clinicopathological parameters like, lymphovascular invasion, tumor stage and lymphnode status, Cyclooxygenase-2 showing down-expression, there is no existence of notable link between the expression of Cyclooxygenase-2 and clinicopathological parameters, including: Age(p=0.197), Tumor grade(p=0.069), Myometrial invasion(p=0.261), Lympho vascular invasion(p=0.516), Lymph node status(p=1000) and Tumor stage(p=0.872). Conclusion: Cyclooxygenase-2 is expressed in a limited number of endometrioid carcinoma and there is lack of significant association between Cyclooxygenase-2 expression and clinicopathological parameters