The current study was conducted to investigate the effect of graded levels of betaine supplementation to the normal and low energy diets of broiler chickens during summer season on growth performance, tonic immobility (TI), economic value and some blood biochemical parameters. Three hundred one days-old broiler chicks were used. The chicks were divided into 6 groups (each of 50 chicks) and each group was 5 replicated (2x3 factorial design). The first, second and third groups were fed normal energy diet (NED) with 0, 1 and 2g betaine/kg diet (air dry basis) for 35 days, respectively. While, the fourth, fifth and sixth groups were fed low energy diet (LED) with 0, 1 and 2g betaine/kg diet (air dry basis) for 35 days, respectively. The experiment was carried out during summer season. Birds freely access to water and feed. Resultsshowedno significant difference of growth performance between NED and LED groups. Betaine supplementation (2g/kg diet) to both NED and LED increased significantly (p < 0.05) the body weight (BW) (1880.61 and 1787.66g, respectively), body weight gain (BWG) (1822.22 and 1728.77g, respectively), feed intake (FI) (3027.36 and 3136.42g, respectively), relative growth rate (RGR) (187.93 and 187.24, respectively) and TI (92.83 and 71.83s, respectively) with no significant difference in feed conversion (FCR) between the groups fed diet supplemented with or without betaine.Betaine supplementation 2g/kg diet to NED increased the total cost, total return, net profit, economic efficiency and performance index%, moreover improved the pancreatic and thyroid function and return the lipids indices of LED-fed birds to the normal level as in the NED-fed birds. No mortalities occur between the different groups.  Therefore, betaine can be included in normal energy diets of broiler chickens by level of 2g/kg diet for improving the growth performance, economic value and welfare during the summer season.