Abstract: Effects of water supplements, sodium bicarbonate (NaHCO3), potassium chloride (KCl) and acetic acid were evaluated on the performance and immune system of chronically heat-stressed broiler chicks. Two hundred day old broiler chicks were allotted to one of the four groups (n = 50); 1) control [no supplements], 2) NaHC03, 0.5%, 3) KCl, 0.15% and 4) acetic acid, 1.5 mL/Liter. All chicks were kept in a controlled environmental chamber maintained at 33±2oC from day one to 6 weeks (wks) of age. Significantly higher weight gains coincided with decreased feed conversion ratios for all the supplemented groups as compared to control group at 2, 4 and 6 wks of age. Bursal index, percentage weights of thymus and spleen in relation to body weight and natural agglutinin levels, an indicator of humoral immunity were higher but the heterophil:lymphocyte ratio, an indicator of stress was lower for the supplemented groups as compared to control group. Total aerobic spore formers and Enterobactraecae counts in the intestinal swab samples were higher in control group than supplemented groups. Intestinal pH was lower at 2, 4 and 6 weeks of age but water consumption at 5 and 6 wks of age tended to be higher in acetic acid treated group as compared to other groups. Overall, the results indicated significant improvement in the performance and immune response of chronically heat-stressed broiler chicks given the water supplements, acetic acid being slightly superior to NaHCO3 and KCl.