A 9‐week‐old, female entire cross breed dog presented with a history of recurrent constipation since being weaned. Survey radiography, CT and subsequently a retrograde vagino‐urethrogram were performed, and the patient was diagnosed with colonic duplication. CT showed a grossly abnormal colon, with the ascending colon bifurcating into two transverse and two descending colons with a common wall between them. During hospitalisation, the patient was observed to pass faecal material from the vulva. A retrograde vagino‐urethrogram was performed and revealed a colovaginal fistula. Surgical intervention was discussed; however, due to the severity of abnormalities found, the owner elected to euthanise the dog. A necropsy confirmed the imaging findings.