The present study was carried out to evaluate the effects of thermoneutral (TN) and high ambient temperature (HAT) on immune response and oxidative status of four broiler strains. Day old broiler chicks (n=242) of four different commercial strains (Ross, Hubbard, Cobb and Arber Acer) were placed in brooding room in first two weeks and then chicks were divided into two groups: TN and HAT zones. Chicks in TN group were housed at constant room temperature, while chicks in HAT zone were kept at high ambient temperature. Chicks in each group were further divided into four sub groups. Each sub group was further subdivided into four replicates having ten chicks per replicate. Blood was collected on weekly basis from day 21 to 42. Mean serum antibody titer against Newcastle disease (ND) and serum paraoxonase (PON1) were significantly higher (P< 0.05) in TN zone, while serum malondialdehyde (MDA) was significantly (P< 0.05) higher in HAT zone. No significant differences were recorded in serum antibody titer against ND, PON1 and MDA among different broiler strains in TN zone, while in HAT zone, Ross and Arber Acer showed significantly (P<0.05) higher serum antibody titer against ND. In HAT zone, significantly (P< 0.05) lower serum MDA was found in Ross and Arber Acer. Based on these results, it was concluded that chronic high ambient temperature has negative effect on broiler immune and oxidative status. Ross and Arber Acer strains were more tolerant to summer high ambient temperature of tropical areas than Cobb and Hubbard.