This research aimed to study the effect of supplementation of Lactobacillus brevis and a combination of Lactobacillus brevis and Enterococus faecalis on growth performance, bacterial population and serum biochemical parameters in broilers. A total of 200 one-day-old chicks were obtained from a local hatchery. They were divided into four groups: group 1 served as a control, group 2 received commercial probiotics, group 3 received Lactobacillus brevis, and group 4 received the combination. The main parameters measured through 6 weeks were body weight, food intake, food conversion ratio (FCR), blood total protein, albumin and cholesterol. In addition to enumeration of bacteria from cloaca and caecum. The results showed a statistically significant increase in body weight (26%) for the group receiving the combined supplementation compared to the control. Similarly, there was a significant increase in FCR for this group compared to the control. The results also showed an increase in the Lactic acid bacteria (LAB) count in the caecum and a decrease in the total late count (TPC) and coliform count, showing the inhibitory effect of LAB. Also, there was a significant decrease in cholesterol and albumin level, while there was no difference between the different groups regarding protein level. The results showed that Lactobacillus brevis and Enterococus faecalis have a good potential to be used as probiotics in poultry.