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Excessive carbohydrate content in aquatic feeds often leads to metabolic disorders in the liver of fish. Probiotics provide an effective means to combat dysregulated glycolipid metabolism in animals. In this study, Lactobacillus plantarum(GDMCC 1.140) was added to assess its efficacy as a probiotic for largemouth bass (Micropterus salmoides) fed a high-starch diet. Three diets, LS representing a normal starch level group (10%), HS representing a high starch level group (20%), and HSP representing a high starch level group supplemented with L. plantarum, were formulated and used to feed juvenile largemouth bass (initial weight 12.54 ± 0.02 g) for nine weeks. The results indicated that there were no significant differences in growth performance or proximate composition among the groups. Subsequently, compared with those in LS group, the fish in HS group exhibited increased hepatic lipid deposition (hepatosomatic index and hepatic lipid), reduced hepatic antioxidant capacity (malondialdehyde) and aggravated liver tissue damage. However, the addition of L. plantarumto the HSP group alleviated or restored relevant indicators to levels comparable to those in LS group. Intestinal microbiota analysis revealed that the alpha diversity of the HS group was significantly lower than that of LS group, with a lower relative abundance of Romboutsiaand a greater abundance of Achromobacter. Notably, the diversity and composition of the HSP group were similar to those of LS group. Furthermore, the hepatic transcriptome analysis revealed that, in the comparison between HSP and HS groups, differentially expressed genes were enriched in the peroxisome proliferator-activated receptor signaling pathway and citrate cycle. In conclusion, the supplementation of L. plantarumin the diet can mitigate liver metabolic disorders in largemouth bass induced by high-starch diets. This research highlights the potential of dietary L. plantarumfor alleviating adverse effects associated with high-starch diets for carnivorous fish.