A 58-year-old man was referred to us because of anal bleeding. Digital rectal examination revealed a 1.2 x 0.8 cm-sessile villous tumor located in the anal canal and lower rectum. Pruritus was lacking and there were no erythematous lesions or any skin lesion in the perianal region. Histologic examination of the excised lesion revealed the presence of an adenocarcinoma within a villous adenoma. The malignancy exhibited well, moderately and poorly differentiated areas with signet-ring cell elements. Because the carcinoma had massively invaded into the submucosa, additional abdominoperineal resection was performed. Microscopic examination of the obtained specimens showed incidental Paget's disease of the anal skin. Although perianal Paget's disease associated with rectal cancer is rare, cautious pathologic examination of the anal and perianal skin in cases with anorectal carcinoma is necessary, even if there are no suggestive clinical findings. If there is perianal Paget's disease, surgical resection with sufficient apparently normal skin and close follow-up are necessary.