Endometrial adenocarcinoma is described in two young intact female Persian cats presented with haemorrhagic vaginal discharge. The discharge had been present for 3 and 15 days in each case, respectively. On the basis of signalment, history, clinical, laboratory and diagnostic imaging findings a tentative diagnosis of pyometra was made in each cat and ovariohysterectomy was subsequently performed. Histological examination revealed endometrial adenocarcinoma in both cats together with ovarian luteal cysts and pyometra in one case. Immunohistochemistry revealed a diffuse and strongly positive reaction for oestrogen receptors in the nuclei of glandular epithelium in well-differentiated areas of the neoplastic tissue. Poorly differentiated areas of solid growth pattern had weak and focal expression of oestrogen receptors. Furthermore, the neoplastic cells within these areas displayed moderate to strong diffuse nuclear staining with Ki-67 antibody suggestive of a high proliferative capacity. The owners reported that the cats were clinically healthy 23 and 21 months after the surgery. These cases highlight the importance of histological examination of surgically resected tissue even when clinical signs and laboratory findings suggest pyometra.