P3HT films were modified by incorporation of different amounts of nickel oxide (NiO). The nickel oxide powder was synthesized by chronoamperometry. The composites were further dissolved and deposited by the spin-coating method on indium-tin oxide (ITO) substrates. Effects of NiO content on the morphology structure and optical properties of P3HT films were investigated by means of XRD, SEM, AFM, and UV-Vis spectroscopy. Electrochemical and photoelectrochemical performances were evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge, and photocurrent measurements. Results show that NiO dispersed uniformly in P3HT thin films and modified the surface roughness and absorption of the deposited thin films. A remarkable improvement of photocurrent density and electrochemical capacitance is observed for an NiO content ranging between 1 and 10wt%. The specific capacitance obtained for P3HT alone is about 20.8Fg(-1), this value increases to 81.4Fg(-1)for the P3HT-NiO 10wt% composite film at 0.1-A/g current density.