CSF3 exerts a significant function in the progression of colorectal cancer (CRC). N6-methyladenosine (m6A) modification is now considered the main driving factor of RNA influence for maintaining homeostasis in cancer cells. Nevertheless, how m6A mediates the role of CSF3 and its influence in pathogenesis of CRC is still elusive. After neutrophil isolation from bone marrow, the purity and survival rate of neutrophils were assessed. Azoxymethane (AOM)/Dextran Sodium Sulfate (DSS) was employed to construct the CRC mice model. Both loss-of-function and gain-of-function experiments were conducted to explore the influence of CSF3 on NETosis and tumorigenesis of CRC in vitro and in vivo. The purity and survival rate of neutrophils were 88.07% and 94.84%, respectively. Overexpression of CSF3 (oe-CSF3) markedly enhanced NETosis, while CSF3 knockdown (sh-CSF3) suppressed it. Intriguingly, CSF3 expression positively correlated with relaxin-2 (RLN2) levels in CRC cells, and RLN2 supplementation rescued tumorigenesis and NETosis after sh-CSF3 treatment. Mechanistically, fat mass and obesity-associated protein (FTO)-mediated m6A demethylation of CSF3 mRNA suppressed CRC tumorigenesis in vivo. CSF3 upregulation counteracted the tumor-suppressive effects of FTO overexpression, restoring NETosis and tumor growth. Consistent with this, FTO overexpression in CRC mice alleviated disease severity, as evidenced by improved body weight, reduced tumor burden, and diminished NETosis. Collectively, our findings establish a novel regulatory axis in which FTO-dependent m6A demethylation of CSF3 suppresses NETosis by inhibiting RLN2 expression, offering new insights into therapeutic targeting of the m6A-CSF3-RLN2 pathway in CRC.