Nickel ferrite [NiFe2O4 (NFO)] nanoparticles were synthesized using a simple precursor based chemical route and modified with tetraethoxysilane (TEOS) to form SiO2 layer adsorbed on the NFO particles (SiO2@NFO). Based on the nanoparticles, the SiO2@NFO-PMMA composite films were prepared embedded with SiO2@NFO nanoparticles in a poly (methylmethacrylate) (PMMA) matrix. The properties of the composites were characterized extensively using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, dielectric and electrical measurement. FTIR analysis showed that the SiO2 groups had been successfully introduced into the NFO nanoparticles. The SEM images of the SiO2 adsorbed NFO nanoparticles had better dispersion in the PMMA matrix than the unmodified one. The SiO2 modified NFO-PMMA composites had much higher dielectric constant and better suppressed dielectric loss than the other two phase composite systems. The maximum dielectric constant was up to ≈ 67 while the dielectric loss was controlled below 0.5. This study suggested that the SiO2 modified NFO-PMMA composite films with high dielectric constant and low loss might be promising candidates for application in microelectronic engineering.