Cubital tunnel syndrome is the most common entrapment of the ulnar nerve. Complications in the treatment of cubital tunnel syndrome may be caused by errors in diagnosis, errors in conservative management, and errors of surgical treatment. This article discusses each cause of complications separately, with a division in errors of surgical treatment into complications from decompression of the ulnar nerve, medial epicondylectomy, anterior transposition of the ulnar nerve, intramuscular transposition of the ulnar nerve, subcutaneous transposition of the ulnar nerve, submuscular transposition of the ulnar nerve, and failed surgical treatment.