In this prospective study, medial humeral epicondylitis was characterized based on anatomic, radiographic, and histologic observations in 60 European shorthair cats that died (or were euthanized) for medical reasons. Elbow instability was not noted in any cats. Radiographs of both elbows were taken using extended craniocaudal and extended and flexed mediolateral projections. Histologic samples from normal elbows and those with new bone formation at the medial epicondyle were compared. Radiographic evidence of medial humeral epicondylitis including chronic degeneration, mineralization, and metaplastic bone formation were noted in 6 cats (10%); 2 had histologic evidence of ulnar nerve displacement and epineural fibrosis. Results suggested that medial humeral epicondylitis is common in cats and has potential clinical sequelae. Active pronation and supination are important movements in cats, especially for climbing and hunting. Whether this predisposes cats to epicondylitis is unknown. Early stage epicondylitis may be overlooked in cats, particularly in the absence of soft tissue mineralization on radiographs.