This work aimed to study the effect of different levels of selenium source (inorganic - organic) on productive performance, physiological responses and blood constituents of broiler chicks under desert conditions. A total number of 240 broiler chicks, day-old sexed males Cobb 500 were randomly divided into eight equal treatments (30 chicks of each) which in turn were divided into 3 equal replicates, 10 chicks each. The 1^st, 2^nd, 3^rd, 4^th treatments (Tr INS1, Tr INS2, Tr INS3 and Tr INS4, respectively), chicks fed inorganic selenium at level of 0.35, 0.30, 0.40, 0.45 mg/kg diet, respectively. The 5^th, 6^th, 7^th and 8^th treatments (Tr ORS5, Tr ORS6, Tr ORS7 and Tr ORS8, respectively), chicks were fed mixture inorganic and organic selenium at level of (0.15+0.20), (0.12+0.18), (0.17+0.23), (0.19+0.26) mg/kg diet, respectively. The (Tr INS1) served as control group. The results showed that, FBW and BWG were significantly increased in broiler chicks of Tr ORS6, Tr INS4, Tr INS2 and Tr ORS8 groups as compared with broiler chicks of control group. Glutathione activity was significantly increased in the chicks fed organic selenium as compared to the chicks fed inorganic selenium groups. Meanwhile, malondialdehyde enzymes (MDA) was decreased (P<0.05) in the chicks fed mixture inorganic and organic selenium as compared to the chicks of control group. In conclusion, the delivery of mixture inorganic and organic selenium at level of 0.30 mg/kg (0.12 mg/kg diet inorganic selenium + 0.18 mg/kg diet organic selenium) diet to broilers is beneficial for growth performance without having negative effect on physiological responses.