A series of 5-substituted-1H-tetrazoles have been efficiently synthesized in moderate to excellent yields (68-90%) under mild reaction conditions by combining aryl aldehydes, hydroxylamine hydrochloride with sodium azide in the presence of catalytic amount of Cu(OAc)(2) in deep eutectic solvent (DES). The new synthetic method has many advantages, such as high conversion, green reaction medium, easy work-up, low cost, and environment friendly. (C) 2018 Elsevier Ltd. All rights reserved.