Pyrroloquinoline quinone (PQQ), a putative essential nutrient and redox modulator in microorganisms, cell and animal models, has been recognized as a growth promoter in rodents. Three separate experiments were conducted to determine the potential effects of pyrroloquinoline quinone disodium (PQQ.Na2) on growth performance and antioxidant defense system of broiler chicks under normal or dexamethasone induced stress conditions. The overall results of this study suggest that dietary PQQ.Na2 (0.2 mg/kg diet) had the potential to act as a growth promoter comparable to antibiotic in broiler chicks under normal production condition. Dietary PQQ.Na2 was more efficiently utilized under low level of stress condition induced by low level of DEX. However, broilers did not receive any extra benefit from provision of higher levels of dietary PQQ.Na2.