OBJECTIVE To describe the radiographic outcome of root canal treatment (RCT) of canine teeth of cats. DESIGN Retrospective case series. ANIMALS 32 cats with 37 canine teeth with complicated crown fractures that underwent RCT. PROCEDURES Medical record databases of 5 referral veterinary hospitals were searched to identify cats that underwent RCT between 1998 and 2016. Only cats that had at least 1 follow-up examination during which radiographs were obtained of the treated canine tooth or teeth were included in the study. Dental radiographs obtained before and immediately after RCT and during all follow-up examinations were reviewed. Treatment was considered successful if the periodontal ligament space was within reference limits and preoperative external inflammatory root resorption (EIRR), if present, had stabilized. Treatment was considered to have no evidence of failure if preoperative EIRR had stabilized and preexisting periapical lucency was stable or decreased in size but had not resolved. Treatment was considered to have failed if periapical lucency or EIRR developed subsequent to RCT or preexisting periapical lucency increased in size or preoperative EIRR progressed following RCT. RESULTS Follow-up time after RCT ranged from 3 to 72 months. The RCT was successful for 18 (49%) of the 37 treated teeth, had no evidence of failure for 12 (32%), and failed for 7 (19%). Preexisting EIRR and patient age ≥ 5 years significantly increased the rate of RCT failure. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that RCT was a viable treatment option to salvage endodontically diseased canine teeth in cats.