Cutaneous findings are common in Costello syndrome, but have not been extensively reviewed in the dermatology literature. We present the cutaneous and histopathologic findings from two cases of Costello syndrome and review previously described cutaneous features of this syndrome. Both patients had manifestations of Costello syndrome with thick, lax skin on the dorsal aspects of hands and feet, deep palmar and plantar creases, curly hair, hyperkeratoses, acanthosis nigricans, papillomas, and multiple pigmented lesions. One patient had multiple syringomas on the forearms, a finding not previously reported. Pigmented lesions have previously been reported as nevi in the literature though no biopsies have been reported. We conclude that thick, loose skin on the dorsal aspects of hands and feet and deep palmar and plantar creases are cardinal manifestations of Costello syndrome and benign tumors of ectodermal origin such as papillomas, calcified epitheliomas, dermoid cysts, mammary fibroadenosis, and syringomas are important features of this syndrome.