Background:Gut microbiota is the complex community of microorganisms that live in the GIT of humans and other animals.Oligofructose(OFS) is one of prebiotics which modulates gut microbiota. Objective:Assessing the potential effects of the prebiotic OFS on gut microbiota and metabolic endotoxemiain high fat diet (HFD) fed rats. Material and methods: Forty adult male albino rats weredivided into 2 groups: Group I (10 rats)fed on a standard rat chow for 14weeks. Group II (30 rats) fed on HFD for 8weeks.In the next 6 weeks, rats of group II were divided into 3 equal subgroups:Group II 1(control B) continued feeding on HFD.Group II 2 continued feeding on HFD with administration of OFS. Group II 3 continued feeding on standard rat chow instead of HFD with administration of OFS. At the end of 14 weeks, blood and fecal samples were collected for biochemical analysisto gut microbiota (FirmicutesandBacteroidetes phyla), lipopolysaccharide (LPS), and tumor necrosis factor alpha (TNFα). Results: OFS produced increase in Bacteroidetes phylum in comparison with HFD fed group (control B). On the other hand, OFS produced decrease in Firmicutes phylum, LPS and TNFα in comparison with HFD fed group (control B). There was better improvement when OFS was given standard rat chow than with HFD. Conclusion: OFS induced improvement in gut microbiota composition, endotoxemiaand inflammatory biomarkers. There was better improvement when OFS was fed with standard diet in HFD fed rats.