The effects of different dietary electrolyte balances (DEB; 220, 230, 240, 250, 260, 270 and 280 mEq/kg of diet) were investigated on growth performance, carcass traits, blood serum parameters and immune responses of broilers under thermoneutral environment. Data were analysed in agreement to a completely randomized design. In the grower period (linear, P =.01) and throughout the study (linear, P <.01) feed, energy and protein intakes decreased by increasing the DEB level. In the starter period, ADG showed the lowest value at 250 DEB level (quadratic, P <.01), whereas in the grower period and throughout the study, ADG decreased (linear, P <.01) by increasing the DEB level. Serum uric acid showed the lowest concentration at 250 DEB level (quadratic, P =.02). The serum triglyceride concentration decreased (linear, P =.02) and concentration of high-density lipoproteins raised (linear, P <.01) by increasing DEB level. Immune response against Gumboro disease tended (P =.09) to raise (linear, P <.01) by increasing the DEB level. No considerable DEB effect was observed on carcass traits and relative organ weights. The DEB values ranging from 220 to 240 mEq/kg could be appropriate to promote broiler growth performance. [ABSTRACT FROM AUTHOR]