IntroductionColorectal cancer (CRC) is one of the leading causes of death and illness in the general population. Although the incidence of CRC is steadily decreasing worldwide, it is being diagnosed more in individuals under 50 years of age. Multiple disease-causing variants have been reported to be involved in the development of CRC. This study aimed to investigate the molecular and clinical characteristics of Thai patients with CRC.MethodsNGS-based multigene cancer panel testing was performed on 21 unrelated patients. Target enrichment was performed using a custom-designed Ion AmpliSeq on-demand panel. Thirty-six genes associated with CRC and other cancer were analyzed for variant detection.ResultsSixteen variants (five nonsense, eight missense, two deletions, and one duplication) in nine genes were identified in 12 patients. Eight (66.7%) patients harboring disease-causing deleterious variants in genesAPC,ATM,BRCA2,MSH2, andMUTYH. One of the eight patients also carried additional heterozygous variants in genesATM,BMPR1A, andMUTYH. In addition, four patients carried variants of uncertain significance in genesAPC,MLH1,MSH2,STK11, andTP53. Among all detected genes,APCwas the most frequent causative gene observed in CRC patients, which is consistent with previous reports.ConclusionThis study demonstrated the comprehensive molecular and clinical characterization of CRC patients. These findings showed the benefits of using multigene cancer panel sequencing for pathogenic gene detection and showed the prevalence of genetic aberrations in Thai patients with CRC.