We reported a case of sigmoid colonic high grade tubular adenomas associated with deposited ova of Schistosoma japonicum. A 76-year-old Japanese man was referred to our colonoscopy due to a positive fecal occult blood test. He had a medical history of schistosomiasis japonica. The colonoscopy revealed that there were two sigmoid colon polyps, approximately 8 mm in diameter. These were removed by endoscopic mucosal resection (EMR). Pathological examination revealed high grade tubular adenomas and deposited some ova of Schistosoma japonicum with severe fibrotic change and granuloma formation in the submucosal layer. Colonic schistosomiasis is a probable independent risk factor for the development of colorectal carcinogenesis.