A 59-yr-old female Nile hippopotamus (Hippopotamus amphibius) was diagnosed and treated for severe dermatitis. Lesions included large areas of depigmentation, erosions, and ulcerations on glabrous skin areas, limbs, and perineal region. Histopathologic lesions included a markedly edematous, focally eroded, ulcerative to necrotic epidermis; foci of keratinocyte apoptosis; and a mixed suppurative dermatitis. Most of the dermal vessels had variable hyalinized walls with plump endothelial cells and frequent intramural neutrophils, and some vessels had vascular thrombi consistent with vasculitis. Culture of the lesions yielded beta-hemolytic Streptococcus, Morganella morgannii, and Enterococcus sp. The hippopotamus was successfully treated with sulfamethoxazole and trimethoprim, amoxicillin, and pentoxifylline for more than 2 mo, and the condition did not recur over the subsequent 16 mo.