This paper reports a comparative study on the influence of pristine and oxidized multiwalled carbon nanotubes on ferroelectricity and dielectric dispersion of a classical ferroelectric of Rochelle salt in a range of 10− 2 − 107 Hz with an amplitude of electric field strength of 2 V/cm. For the study, phase transition, polarization switching, frequency dependencies of dielectric permittivity and electrical conductivity of two composites based on Rochelle salt combined with each of the fillers were considered at different temperatures. Fourier-transform infrared spectroscopy was employed to explore the influence of fillers on the functional groups of Rochelle salt. The morphologies of the samples were examined using scanning electron microscopy. It was revealed that the oxidized form of multiwalled carbon nanotubes showed less influence on the dielectric dispersion, but stronger effect on the phase transition and polarization switching than those of pristine ones. At the same time, the high electrical conductivity of both carbon nanotubes resulted in a strong dielectric dispersion and overshadowed the contribution of functional groups of Rochelle salt. Theoretical models will also be used to analyze experimental data.