Liver failure is a serious hepatic dysfunction with high mortality. This work aimed to investigate the effect of a famous probiotic and drug, Lactobacillus reuteri DSM 17938, on liver failure in rats. Sprague-Dawley rats were gavaged with 3 × 10⁹ CFU of DSM 17938 for 7 days. d-galactosamine was intraperitoneally injected to induce acute liver failure on the eighth day. Samples were collected to determine the liver function, serum cytokines levels, terminal ileum and liver histology, gut microbiota, metabolome and transcriptome. Our results showed that pretreatment with DSM 17938 not only reduced the elevation in serum alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, IL-1α, IL-2, IL-18, M-CSF, and MIP-3α levels but also alleviated histological abnormalities of both the terminal ileum and liver induced by d-galactosamine. Additionally, DSM 17938 reduced d-galactosamine-induced enrichment of some taxa of gut Actinobacteria or Firmicutes, including abundant pathogens such as Actinomycetales, Coriobacteriaceae, Staphylococcaceae and Enterococcaceae. Furthermore, DSM 17938 reduced the d-galactosamine-induced increase in not only fecal metabolites such as trisaminol and lithocholic acid but also the transcription of liver inflammatory genes, such as Ccl2, Ccl7, Ccl11, Ccl12, Il6, Il11, Il20rb, Mmp3 and Mmp10. Downregulation of retinol metabolism and PPAR signaling pathway as well as upregulation of viral protein interaction with cytokine and cytokine receptor and central carbon metabolism in cancer signaling pathway were involved in the mechanism of L. reuteri DSM 17938 alleviating liver failure. Our findings suggested that DSM 17938 is a potential probiotic for the prevention or treatment of liver failure.