The poly(1,5-naphthalenediamine-co-aniline) has been synthesized by chemical oxidative polymerization method in an acidic medium. The copolymer with different counter ions (HCL, H2SO4, CH3COOH and HNO3) has been investigated. The newly synthesized copolymers were characterized by UV-visible, FT-IR, fluorescence, H-1 NMR, cyclic voltammetry, TGA and SEM studies. Conductivity studies of the copolymer with various counter ions were also carried out and found to be in the region of semiconductor. Morphological study revealed that the copolymer formed into hollow spheres with smooth surface. Moreover, a detailed reaction mechanism has been postulated for the formation of target copolymer. (C) 2012 Elsevier B.V. All rights reserved.