Abstract: The objective of this study was to establish the dielectric properties of CoFe₂O₄ nanoparticles with particle sizes that varied from 28.6 to 5.8 nm. CoFe₂O₄ nanoparticles were synthesized using a chemical coprecipitation method. The particle sizes were calculated according to the Scherrer formula using X-ray diffraction (XRD) peaks, and the particle size distribution curves were constructed by using field-emission scanning electron microscopy (FESEM) images. The dielectric permittivity and loss tangents of the samples were determined in the frequency range of 1 kHz to 1 MHz and in the temperature range of 300 to 10 K. Both the dielectric permittivity and the loss tangent were found to decrease with increasing frequency and decreasing temperature. For the smallest CoFe₂O₄ nanoparticle size, the dielectric permittivity and loss tangent exhibited their highest and lowest values, respectively. This behavior is very useful for materials used in devices that operate in the microwave or radio frequency ranges.