Policy1-Bowel is a microsimulation model that simulates the adenoma-carcinoma pathway and the serrated pathway in colorectal cancer development, as well as bowel cancer screening. The natural history component of Policy1-Bowel was adapted from the Adenoma and Serrated pathway to Colorectal Cancer (ASSCA) model to the Australian setting. The model simulates the development of colorectal cancer from conventional adenomas, hyperplastic polyps (HP), and sessile serrated adenomas (SSA). The location, shape, size, degree of dysplasia, and architecture of conventional adenomas and the location and size of SSAs and HPs are modelled. Policy1-Bowel has been comprehensively and systematically calibrated to pre-cancer data from the COCOS trial and colorectal cancer and bowel screening-related data in Australia. The model has been used to evaluate a range of bowel cancer screening strategies, including the use of alternative screening technologies other than immunochemical faecal occult blood test (iFOBT), extending National Bowel Cancer Program (NBCSP) target screening age range to include younger and/or older ages, and alternative colonoscopy surveillance management. Findings of these evaluations were used to inform the screening-related recommendations of 2017 Clinical Practice Guidelines for the Prevention, Early Detection and Management of Colorectal Cancer, and have been published in international cancer journals. Policy1-Bowel can also used to complete economic analyses of public awareness campaigns aimed at improving NBCSP participation. The model platform can be adapted to evaluate bowel cancer screening and surveillance strategies in population subgroups or in different countries.