This study was conducted to determine the effect of dietary fat supplementation in body fluids compartments, respiration rate (RR) and rectal temperature (Rt) of broilers during heat exposure. One hundred and twenty (1- day – old) unsexed Sasso chicks were divided randomly into 4 groups. The first group was fed a control diet and kept under normal ambient temperature (28^oc). The second group was fed the control diet and exposed to 40^oc for 3 hrs. at 49 days  of age. The third group was fed the control diet supplemented with corn oil (6%). The fourth group was fed the control diet supplemented with (6%) corn oil and exposed to 40 ^oc for 3hrs. at 49 days of age. Body fluids compartments, respiration rate and rectal temperature were measured. Results indicated that rectal temperature and respiration rate increased during heat exposure in broilers fed diet with or without fat supplementation. Fat supplementation diet decreased total body water % (TBW%) of broilers with or without heat exposure. Heat exposure (40^oc) decreased the percentage of plasma volume (PV%) in broilers. Fat supplementation prevent the reduction of P.V%. In occlusion, the maintenance of plasma volume % in broilers via dietary fat supplementation is an adaptive mechanism to heat stress.