Probiotics exert numerous beneficial effects by regulating gut microbiota composition and are considered a promising nutritional strategy for ameliorating lipid metabolism disorders. This study evaluated the beneficial effects of Lactiplantibacillus plantarum FS5-5, a candidate probiotic with lipid-lowering ability, on diet-induced lipid metabolism disorders. The results showed that strain FS5-5 significantly decreased weight gain, fat coefficient, and lipid levels while alleviating liver oxidative stress damage in high-fat diet (HFD) mice. Serum metabolomics results showed that L. plantarum FS5-5 modulated lipid metabolism, particularly in linoleic acid metabolism, α-linolenic acid metabolism, and primary bile acids biosynthesis pathways. Mechanism analysis suggested that L. plantarum FS5-5 promoted fatty acid β-oxidation by regulating the expression of key genes in the lipid metabolism pathway, including Fxr, Fgf15, Shp, Pparγ, Pgc1α, etc. This effectively reduced several medium/long-chain acylcarnitines levels in serum and promoted fat breakdown. Further analysis showed that the abundance of gut-beneficial bacteria was increased, and intestinal permeability and barrier damage were alleviated after FS5-5 intervention. Spearman correlation analysis showed that several specific genera were notably associated with HFD-related indicators. These findings demonstrated that L. plantarum FS5-5 was a potential functional food for preventing lipid metabolism disorders.