Objective: In this study the effect of Royal jelly on the growth of two important members of Bacteroides spp.; Bacteroides fragilis and Bacteroides thetaiotaomicron, was evaluated. Also the physicochemical properties and cytotoxicity effects of Royal jelly on Caco-2 cell line as gastrointestinal epithelial cell model, assessed. Methods : Bacteria, Bacteroides fragilis and Bacteroides thetaiotaomicron were grown on brain heart infusion (BHI) broth medium supplemented with Royal jelly in 3 different concentrations (2.5, 5 and 10% v/v), both of the bacteria (1.5×108 cfu/mL) were inoculated to BHI broth contained Royal jelly in anaerobic condition. To calculate the bacterial optical density (OD), the absorbance was measured at 600 nm after an overnight. Also Caco-2 cells, was used to study the effects of Royal jelly on epithelial cell viability, and the Physicochemical properties consist of total proteins, polysaccharides, phenolic compounds, total lipids, ash and moisture by UV-VIS spectrophotometric and gravimetric methods were evaluated . Results: The growth of B. fragillis and B. thetaiotaomicron were increased by Royal jelly (2.5, 5 and 10% v/v concentrations) and the results indicated that Royal jelly increased the growth of bacteria in a dose dependent manner (p