Polyaniline (PANI) nanocomposites embedded with manganese iron oxide (MnFe2O4) nanoparticles were prepared as thin films by electropolymerizing aniline monomers onto indium tin oxide (ITO) glass slides pre-spin-coated with MnFe2O4 nanoparticles. The shift of the characteristic peaks of PANI/MnFe2O4 in UV-visible absorption spectra and Fourier transform infrared (FT-IR) spectra indicates the formation of composite films and the chemical interaction between the PANI matrix and MnFe2O4 particles. A coloration efficiency of 92.31 cm2 C-1 was obtained for the PANI/MnFe2O4 nanocomposite film, higher than that of the pristine PANI film, 80.13 cm2 C-1, suggesting a synergistic effect between the MnFe2O4 particles and the PANI matrix. An enhanced areal capacitance of 4.46 mF cm-2 was also achieved in the PANI/MnFe2O4 nanocomposite film compared with 3.95 mF cm-2 in the pristine PANI film by CV at a scan rate of 5 mV s-1. The enhanced performances of the composite films were attributed to the pseudocapacitive properties of MnFe2O4 and rougher morphology caused by the embedment of MnFe2O4 particles into the PANI matrix. Finally, the sulfuric acid (H2SO4) concentration and temperature effects on the supercapacitive behavior of the pristine PANI and PANI/MnFe2O4 nanocomposite films were studied, suggesting the positive effects of decreasing H2SO4 concentration and increasing temperature in a low temperature range; higher temperatures can destroy the PANI structure and cause the degradation of PANI.