The study aimed to evaluate the impact of different levels of betaine and thyme oil as growth promoters in broiler chickens. 600 broiler chickens (Cobb 500) a total number for experimental design at 1day of age were randomly chosen and distributed into 10 groups (60 broilers chickens / each group), that were fed different doses of betaine and thyme oil, except for the control group. broiler chickens of each group were nearly equal in averages body weight from one day of age. Each group sub-divided into three replicates, each of 20 broiler chickens. The experimental group was processed broiler chickens under similar hygienic and environmental conditions as the control group. Broiler chickens were housed in floor systems, and experimental treatments significantly improved growth performance and cecum properties comparison the control group, liver function, triglycerides, total cholesterol, hormones markers and immune and growth response genes). The highest live body weight of EG10 and EG9 groups were (2046.08 and 2009.75 g) as well as found in other experimental group when comparison the CG1 group (1789.5 g) in a row. Moreover, feed conversion ratio of EG10 and EG9 groups were (1.48 and 1.51) as well as found in other experimental group when comparison the CG1 group (1.70). While EG10, EG9 and other experimental group when comparison the CG1 group had a significant enrichment effect on the intestinal beneficial bacteria. The study concluded that the most effective interaction between betaine 500 mg and the experimental group ten had the most significant effect and thyme oil (50 mg) in liter as well as interaction between betaine 250 mg and thyme oil (50 mg) in liter of water has highly significant effect on live body weight and FCR. The study demonstrated a significant positive impact on blood physiology in experimental groups EG10, EG9, EG2, and other experimental groups respectively comparison the control group (CG1) without any significant side effects on broiler chickens.