Abstract: Fusobacterium nucleatum (Fn) has been linked to colorectal cancer (CRC). Several studies showed an overabundance of Fn in human CRC and elucidated the possible mechanisms of Fn involved in CRC in vitro and in mouse models. The mechanisms of Fn involved in CRC carcinogenesis mainly include immune modulation by increasing myeloid-derived suppressor cells and decreasing natural killer cells, toxic effect mediated by FadA, Fap2, and lipopolysaccharide, increasing tumor-associated microRNAs (such as miR-21), and metabolism modulation. This article reviews the mechanisms of Fn in CRC.