Lynch syndrome is associated with pathogenic variants in 4 mismatch repair (MMR) genes that increase lifetime risk of colorectal cancer (CRC). Guidelines recommend intensive CRC surveillance with colonoscopy every 1–2 years starting at 25 years for all carriers of Lynch syndrome-associated variants, regardless of gene product. We constructed a simulation model to analyze the effects of different ages of colonoscopy initiation and surveillance intervals for each MMR gene (MLH1, MSH2, MSH6, and PMS2) on CRC incidence and mortality, quality-adjusted life-years (QALYs), and cost.