In this study, cupric oxide–polyaniline (CuO–PANI) composite was prepared by two-step methodology. First step was involved in the synthesis of PANI by the chemical oxidative polymerization of aniline in the presence of (NH$_4)_2$S$_2$O$_8$ as an oxidizing agent. In the second step, 25 mg of PANI was used as template for making a composite with CuO by hydrothermal method. The crystalline phase, morphology and composition of composite material were investigated by the powder X-ray diffraction and scanning electron microscopy techniques. The composite material contained the monoclinic phase of CuO and some poor diffraction patterns of PANI. The composite material exhibits a flower-like morphology. The CuO–PANI composite was deposited on the glassy carbon electrode and used for the electrochemical determination of hydrochlorothiazide (HCT) in Britton–Robinson (B–R) buffer pH 4.0 by the cyclic voltammetry. The HCT has shown a well resolved anodic peak at 1.20 V against Ag/AgCl reference electrode. The electrode kinetics was diffusion controlled and irreversible in nature. The CuO–PANI composite possessed a linear from 8 to 52 ${\mu}$M HCT concentration with a regression coefficient of 0.99. The limit of detection of the CuO–PANI composite was obtained as 0.8 ${\mu}$M for the HCT. The CuO–PANI composite is highly selective, stable and sensitive for the HCT. Therefore, we believe that the newly prepared CuO–PANI composite material can be useful for the different electrochemical applications.