Background <p>Gut microbiota and its metabolites are revealed to affect metabolic dysfunction-associated fatty liver disease (MAFLD) progression. Precedingly, we proved bifidobacterium bifidum BGN4 fractions declined sterol regulatory element-binding transcription factor 1 (SREBP1) to suppress ferroptosis during MAFLD. This study explored whether agmatine, a key metabolite induced by BGN4, affected MAFLD development.</p> Methods <p>High-fat diet (HFD)-fed mice or palmitate (PA)-stimulated MIHA hepatocytes were treated with agmatine. General conditions of the mice were evaluated by behavioral tests, body weight, liver weight, and plasma biochemical parameters, while hepatic steatosis was observed with H&amp;E staining. Hepatocyte cytotoxicity was assessed by lactate dehydrogenase assay, and mitochondrial dysfunction was evaluated with ATP content and oxygen consumption rate. Ferroptosis was estimated by lipid peroxidation, iron, and expressions of related proteins. Immunohistochemistry, immunofluorescence, western blot, and RT-qPCR were used for detecting protein and mRNA levels. Molecular mechanism was investigated using RNA immunoprecipitation, methylated RNA immunoprecipitation, luciferase reporter assay, and RNA stability assay.</p> Results <p>In the HFD-induced MAFLD mouse model, agmatine treatment alleviated metabolic abnormalities, depression-related behavior, hepatic damage, and ferroptosis, and decreased Iba1 and GFAP in cortex. In the in vitro model of PA-induced hepatocytes, agmatine mitigates cytotoxicity, mitochondrial dysfunction, and ferroptosis. Increases of SREBP1, RNA binding motif protein 15 (RBM15), and IGF2 mRNA binding protein2 (IGF2BP2) in MAFLD models were rescued by agmatine. RBM15/IGF2BP2 knockdown inhibited m⁶A modification and stability of SREBP1 mRNA. SREBP1 overexpression neutralized the protective role of agmatine, which was overturned by silencing RBM15/IGF2BP2.</p> Conclusion <p>Agmatine relieved MAFLD via inhibiting RBM15/IGF2BP2-mediated SREBP1 m⁶A modification.</p>