DHA-rich microalgae oil supplementation reduced hepatic triglycerides and serum LDL cholesterol while increasing HDL levels in high-fat diet-fed mice over 8 weeks. The intervention enriched beneficial gut bacteria including Lactobacillus and Bifidobacterium while reducing inflammatory taxa like Clostridium and Ruminococcus. Metabolomic analysis revealed altered microbial pathways affecting methionine metabolism and phenylethylamine degradation. This research positions marine-derived DHA as a dual-action therapeutic targeting both liver metabolism and gut microbiome dysfunction simultaneously. The gut-liver axis connection suggests omega-3 fatty acids may work through microbial intermediates rather than direct hepatic effects alone. However, the small sample size (n=4 per group) and short intervention period limit clinical translation. The microalgae source offers advantages over fish oil including sustainability and reduced contamination risk. For adults with fatty liver disease, this mechanistic insight supports combining omega-3 supplementation with microbiome-supporting strategies. The findings are confirmatory of DHA's metabolic benefits but novel in demonstrating specific microbial pathway modifications that may explain the therapeutic mechanisms.