The incidence of multiple primary malignancies (MPMs) associated with colorectal cancer (CRC) varies, ranging from 3.0% to 17.0%, with synchronous MPMs occurring at rates of 1.0% to 4.41%. The incidence of MPMs was found to be higher in male and older CRC patients. However, age-related findings are inconsistent, with some studies indicating a higher risk in younger CRC patients, possibly linked to genetic aberrations and carcinogen exposure. The field cancerization theory, chemotherapy, and radiotherapy demonstrated associations with the occurrence of MPMs. Genetic analyses emphasizing microsatellite instability (MSI), CpG island methylation phenotype (CIMP), chromosomal translocations, and p53 mutations as potential contributors to the development of MPMs associated with CRC. Prognostically, MPMs associated with CRC, especially synchronous cases, are linked to lower survival rates, primarily attributed to postoperative complications.