This paper presents the physicochemical, conductive, and electrochemical properties of different polyaniline (PANI)-derived polymer/Al2O3 nanocomposites synthesized by chemical oxidation polymerization method carried out in two stages: first, activation of the surface of the Al2O3 nanoparticles by hydrochloric acid and second, polymerization of 2-chloroaniline (2ClANI), aniline (ANI), and the copolymer (2ClANI-ANI) in the presence of Al2O3 by using ammonium persulfate as oxidant in aqueous hydrochloric acid. XRD and TEM results reveal the growth of the polymers on Al2O3 nanoparticles and the formation of PANI-derived polymer/Al2O3 nanocomposites. FTIR and UV-Vis show a systematic shifting of the characteristic bands of the polymers with the presence of Al2O3 nanoparticles. Moreover, these nanoparticles enhance the thermal stability of the polymers, as found by thermogravimetric analysis (TGA). Although the incorporation of Al2O3 nanoparticles reduces the electric conductivity of the polymers, the resulting nanocomposites still keep high conductivities, ranging between 0.3 × 10−2 and 9.2 × 10−2 S cm−1. As a result, the polymer/Al2O3 nanocomposites exhibit a good voltammetric response. All these synergetic features of the nanocomposites are assigned to the effective interaction of the polymers and Al2O3 particles at nanoscale. ; This work was supported by the National Assessment and Planning Committee of the University Research (CNEPRU number E-03720130015), the Directorate General of Scientific Research and Technological Development (DGRSDT) of Algeria. The financial support from MINECO is also acknowledged (MAT2013-42007-P project).