Colorectal cancer (CRC) is the second-leading cause of cancer-related death in the United States. Approximately 10% of CRC is hereditary, and hereditary nonpolyposis CRC (HNPCC), or Lynch syndrome I, is the most common form. Lynch syndrome I is characterized by onset at an early age, poor differentiation, predominance of proximal tumors, and an excess of synchronous and metachronous tumors. In Lynch syndrome II, patients exhibit Lynch syndrome I features and also have extracolonic cancers. Lynch syndrome is an inherited autosomal dominant disorder caused by a germline mutation in one of several genes responsible for DNA mismatched repair. Amsterdam I criteria, Amsterdam II criteria, and Bethesda guidelines are the international diagnostic criteria for Lynch syndrome. Nursing care for patients with Lynch syndrome includes identifying patients who would benefit from genetic counseling, providing education, and assessing and meeting patient psychosocial needs.