Cohen syndrome is a rare genetic disorder consisting of truncal obesity, hypotonia, mental retardation, microcephalia, characteristic facial appearance and ocular anomalies. Other diagnostic clinical features include narrow hands and feet, low growth parameters, neutropenia and chorioretinal dystrophy. Acanthosis nigricans is a cutaneous disorder characterized by hyperpigmentation and papillomatosis. Syndromal acanthosis nigricans may occasionally appear as a feature of several specific syndromes. We report a patient showing the typical characteristics of Cohen syndrome with acanthosis nigricans and hyperinsulinemia.