Background: Given the rise in colorectal cancer (CRC) in younger patients, this study aims to analyze the radiation exposure received by early onset colorectal cancer patients from diagnostic imaging performed in the first 5-years from diagnosis. Methods: A retrospective review of all patients (age ≤ 50 y) with stage I-III CRC who received at least 5 surveillance or staging body computed tomography (CT) scans in the 5 years from diagnosis was performed beginning in October 2015. The volume CT dose index (CTDIvol) and dose length product (DLP) were extracted; a previously validated Monte Carlo (MC) based software, VirtualDose (Virtual Phantoms, Inc., Albany, NY), was used to estimate organ dose to 19 organs based on the imaging mode parameters. The effective doses were calculated based on methods set forth in the International Commission on Radiological Protection ICRP No. 103 Publication. Results: A total of 107 patients were included (age range 25-50 years, median 44 years). The average effective dose per CT scan was 15.0 mSv range: 11.6 to 22.6 mSv) for male (n = 62) and 13.4 mSv (8.04 to 17.5 mSv) for female (n = 45) patients. The cumulative effective dose was greater than 100 mSv for 9 (8.4%) of patients and between 50 to < 100 mSv for 28 (26.2%) of the patients in this study. Of the 107 patients, 23% (n = 25) of the patients recurred during the first 5 years. Conclusions: The majority of early-onset colorectal cancer patients in this study received a cumulative dose under 100 mSv, which is considered low risk according to a policy statement by the International Organization for Medical Physics. Since the majority of patients in this study received what is considered a low cumulative radiation dose from repeated CT imaging during the 5-year period after diagnosis, this may provide reassurance that repeated CT imaging, particularly for surveillance, is warranted. Individual risk will vary but the clinical benefits of clinical imaging outweigh the small, if any, risk of radiation-induced cancers in this patient cohort.