Dysbiosis in the gut microbiota plays a significant role in GI cancer development by influencing immune function and disrupting metabolic functions. Dysbiosis can drive carcinogenesis through pathways like immune dysregulation and the release of carcinogenic metabolites, and altered metabolism, genetic instability, and pro-inflammatory signalling, contributing to GI cancer initiation and progression. infection and genotoxins released from dysbiosis, lifestyle and dietary habits are other factors that contribute to GI cancer development. Emerging diagnostic and therapeutic approaches show promise in colorectal cancer treatment, including the multitarget faecal immunochemical test (mtFIT), standard FIT, and faecal microbiota transplantation (FMT) combined with PD-1 inhibitors. We used search engine databases like PubMed, Scopus, and Web of Science. This review discusses the role of dysbiosis in GI cancer onset and explores strategies such as FMT, probiotics, and prebiotics to enhance the immune response and improve cancer therapy outcomes.