Two unusual cases of symptomatic partial rupture of the extensor carpi ulnaris tendon associated with ulnar-styloid nonunion are described. Intraoperative findings suggested that the jagged surface of the distal ulna was the cause of flaying. In one case, debridement of the frayed extensor carpi ulnaris tendon and fixation of the ulnar styloid were effective for the relief of symptoms. But after the same procedure in another case, osteosynthesis of the ulnar-styloid could not be attained and tenodesis of the extensor carpi ulnaris tendon to the ulnar head was needed. Partial rupture of the ECU tendon should be taken into account in the differential diagnosis of a patient with ulnar wrist pain after ulnar-styloid fracture.