We report the synthesis and pseudocapacitive studies of a composite film (PANI-ND-MnO2) of polyaniline (PANI) and manganese oxide (MnO2) nanoparticles. To enhance the interaction of MnO2 and PANI, the surfaces of MnO2 nanoparticles were modified by a silane coupling reagent, triethoxysilylmethyl N-substituted aniline (ND42). The composite film was obtained via controlled electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of MnO2 nanoparticles (ND-MnO2) on a carbon cloth in a electrolyte of 0.5M H2SO4 and 0.6M (NaPO3)6. In comparison to similarly prepared PANI film, the incorporation of MnO2 nanoparticles substantially increases the effective surface area of the film by reducing the size of rod-like PANI aggregates and avoiding the entanglement of these PANI nanorods. Significantly, we observed significant enhancement of specific capacitance in PANI-ND-MnO2 film compared to PANI–MnO2 film prepared in a similar condition, indicating that the presence of the coupling reagent can improve the electrochemical performance of PANI composite film. A symmetric model capacitor has been fabricated by using two PANI-ND-MnO2 nanocomposite films as electrodes. The PANI-ND-MnO2 capacitor showed an average specific capacitance of ∼80Fg−1 and a stable coulombic efficiency of ∼98% over 1000 cycles. The results demonstrated that PANI-ND-MnO2 nanocomposites are promising materials for supercapacitor electrode and the importance of designing and manipulating the interaction between PANI and MnO2 for fundamentally improving capacitive properties.