A 13-year-old castrated male Shih Tzu was presented with recurrent otitis externa and ulcerative dermatitis. Previous investigations had failed to identify the cause, and the lesion was resistant to treatment. According to the histopathological examination, a tentative diagnosis of chronic ulcerative dermatitis with bacterial infection was made. To treat the patient, immune cell therapy with antibiotics was conducted every 2 weeks, for a total of six sessions. After treatment, the skin lesion resolved. No side effects were observed during therapy. To the best of our knowledge, this is the first case report of the use of immune cell therapy for canine ulcerative dermatitis.