Abstract: An experiment was carried out to study the effect of CoQ10 supplementation at 20 and 40 mg kg–1 in high energy diets under higher environmental temperature. The trial was carried out with 216 days old Cobb 400 broiler chicks divided into four treatments with nine replicates containing six birds in each. The treatments include normal energy diet (NE) (G1) (as per breeder’s specifications) and high energy (HE, Normal energy plus 100 kcal) diet without (G2) and with CoQ10 supplementation at 20 (G3) and 40 (G4) mg kg–1. The Temperature Humidity Index (THI) during the study ranged from 24.46-33.05°C. The bird’s growth performance, feed intake, feed efficiency, its serum lipid, mineral profile, serum antioxidant activity, muscle lipid and CoQ10 content, slaughter parameters cost of live weight gain were studied. There was no significant difference in the body weight gain, feed intake, feed efficiency in the growth periods and slaughter parameters among the treatment groups, whereas the production score, higher intestinal length and better feed cost per kg of live weight gain was observed in NE fed groups than the other three groups. The serum and muscle lipid content was reduced and serum antioxidant activity was increased with on CoQ10 supplementation at 20 and 40 mg kg–1 in the diet.