Modulating the intestinal microbiota of birds by using probiotics and prebiotics to reduce mortality and increase poultry health is a method of interest in the poultry industry. This study aimed to determine the best combination of synbiosis between Enterococcus faecium and one of the four prebiotics: mannan oligosaccharide (MOS), oligofructose (OF), xylooligosaccharide (XOS) or galactooligosaccharide (GOS). Based on the results of laboratory studies, a synbiotic was selected for performance evaluation in broiler chickens. Based on the results of in vitro studies, E. faecium + GOS combination was selected for further study as a potential synbiotic. Four hundred broiler chickens of the Cobb 500 breed were randomly assigned to 4 experimental treatments, and each repetition had 20 birds of one-day-old chickens, males, and females. Experimental treatments included control, control + prebiotic GOS, control + E.faecium probiotic, and control + selected synbiotic. After six weeks of feeding, growth performance, immune response, and intestinal microbiota were evaluated. Administration of GOS and E.faecium as synbiotic positively affected performance, especially in the first periods of production (P < 0.05). Treatments containing synbiotic and prebiotic significantly reduced the population of E. coli compared to the control treatment (P < 0.05). These results showed that E.faecium + GOS can be an efficient synbiotic for broiler chickens. However, determining the selected synbiotic effects on challenged broiler chickens is a point of interest that merits further research.