In the present work, cobalt ferrite nanoparticles were synthesized by the combustion method using two different fuels, urea and citric acid. The fuels were altered to vary the size and also to study the effect of the fuel and size on the dielectric and magnetic properties of cobalt ferrite. The phase formation was confirmed by powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The average crystallite size of the particles was calculated using Scherrer’s formula, and it was observed that the particles were of nanosize ranging from 10 to 13 nm. The surface morphology and chemical composition of the compounds were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The influence of fuel on the dielectric study and conductivity was determined at different temperatures (35–120 °C) and also at different frequencies (10 Hz–5 kHz). An increase in the dielectric constant, saturation magnetization (Ms), coercivity (Hc), and remanent magnetization (Mr) was observed with an increase in the particle size. © 2016, Springer Science+Business Media New York.