Abstract: This study aims to investigate the impact of Bacillus subtilis-fermented dandelion herbal products on growth performance, immune function, and intestinal health in aquatic organisms by using grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatu ♂) as the model species. The groupers were divided into two cohorts: a control group fed a basal diet and a supplemented group the basal diet with fermented herbal additive for 56d. Post-experimentation, samples were collected to analyze relevant parameters. The findings indicated that the incorporation of a fermented Chinese herbal additive significantly improved weight gain rate (WGR), specific growth rate (SGR), condition factor (CF), and survival rate in response to Photobacterium damselae subsp. piscicida infection (P<0.05), while concurrently achieving a significant reduction in the feed conversion ratio (FCR) (P<0.05). The supplemented group exhibited markedly higher intestinal lipase (P<0.01) and protease activities (P<0.05). Moreover, gene expression analysis revealed downregulated fatty acid synthesis genes, alongside an upregulated glycolysis and lipid catabolism genes. The Ace and Chao1 indices of the intestinal microbiota increased significantly (P<0.05), with an observed upregulation in microbial metabolism and biosynthesis compared to the control group (P<0.05). Additionally, there was a significant augmentation in the activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), reduced glutathione (GSH), and lysozyme (LZM) within the intestine (P<0.05), accompanied by downregulated pro-inflammatory factors, upregulated anti-inflammatory factors, and reduced apoptotic factors In serum, the additive significantly decreased alanine aminotransferase (ALT) activity (P<0.01) and increased lysozyme (LZM) and alkaline phosphatase (AKP) activities (P<0.01). Hepatic tissue showed a notable increase in the activities of reduced glutathione (GSH) and catalase (CAT) (P<0.05), alongside a substantial enhancement in total antioxidant capacity (T-AOC) (P<0.01). The additive facilitated hepatic glycolysis, diminished fatty acid synthesis, and augmented lipid catabolism. Furthermore, it downregulated inflammatory mediators, upregulated anti-inflammatory mediators, and decreased apoptotic factors. In conclusion, incorporation of Bacillus subtilis-fermented traditional Chinese medicine products into grouper feed facilitates fish growth, augments non-specific immune responses and antioxidant capacity, increases diversity and abundance of potentially beneficial bacteria, and maintains intestinal health. This study establishes a theoretical foundation for the utilization of probiotic-fermented Chinese herbs as additives in aquatic feeds as a safe and efficient alternative to antibiotic growth promoters, potentially reducing farming costs, minimizing drug residues and resistance issues, and fostering sustainable green aquaculture practices.