A 9-year-old, castrated male, miniature schnauzer presented with malaise, anorexia, fever and severe inflammatory skin lesions on the dorsum, thighs and pinnae. The lesions developed 2 days after bathing with a commercial shampoo. Histopathological examination of skin samples revealed neutrophilic exocytosis, parakeratosis, epidermal hyperplasia and neutrophilic infiltration in the superficial dermis. Skin lesions resolved completely after 14 days of treatment with prednisolone and ofloxacin. Patch testing performed on the patient and a clinically healthy dog showed erythema at the site exposed to the culprit shampoo 48 h later only on the patient. Histopathological findings of the erythematous reaction were similar to those of the spontaneous skin lesions. Based on these findings, the dog was diagnosed with superficial suppurative necrolytic dermatitis of miniature schnauzers. The patch test results suggested that contact dermatitis to a commercial shampoo played a role in the pathogenesis of this disease.