A 10-year-old male castrated European Shorthair was presented with signs of scaling, alopecia and pruritus. Thedermatopathological examination demonstrated an interface dermatitis with a few apoptotic keratinocytes, a murallymphocytic folliculitis and the absence of sebaceous glands. These skin changes are compatible with a paraneoplasticsyndrome caused by a thymoma. A thoracic radiograph confirmed the presence of a mass in the cranial mediastinum.A sternal thoracotomy was performed. One large tumor and two smaller masses were removed. Histopathologicalexamination of the masses revealed a lymphocyte-rich thymoma. Initially, the skin lesions improved significantly.A few weeks after surgery, there was a relapse of the exfoliative dermatitis, which regressed with a dexamethasonetreatment. On the last follow-up consult, 6 months post-operatively, the cat was no longer administered anymedication and only showed mild scaling and no pruritus.