Endometrial polyps are rare benign uterine masses exclusively reported in geriatric, entire, female dogs or spayed female dogs with ovarian remnant syndrome. A 12‐year‐old, female, ovariohysterectomised cocker spaniel was presented for hyporexia, progressive muco‐haemorrhagic vulval discharge, and an ultrasonographically detected caudal abdominal mass. Thoracic and abdominal computed tomography revealed that the mass originated from the uterine stump, with no evidence of metastasis. Surgical excision of the mass was performed, and histopathology of the mass was consistent with an endometrial polyp. The dog was confirmed to be neutered based on the absence of ovarian remnant found on computed tomography and during surgery, and the negative results of both anti‐Mullerian hormone test and human chorionic gonadotropin stimulated progesterone test. The dog fully recovered with complete resolution of clinical signs at 2‐week, 6‐month and 18‐month rechecks. The presenting case highlights the first reported case of an endometrial polyp in a spayed female dog.