Generalized idiopathic acanthosis nigricans is a rare form of acanthosis nigricans. This form may be familial or nonfamilial and begins at birth or in early childhood. We report an 18-year-old boy with generalized idiopathic acanthosis nigricans who has no family history of acanthosis nigricans. The patient was treated with oral acitretin. Acitretin has been reported rarely as a therapeutic retinoid agent in the disease to date.