As a promising material for soft magnets, cobalt doped manganese ferrite [Mn(1-x) CoxFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5)] nanoparticles were prepared by two methods (conventional combustion and microwave assisted combustion technique). Nitrates of the constituent elements and urea were respectively used as the oxidizer and fuel to drive the reaction. The effect of microwave irradiation on the phase composition, microstructure, magnetic and optical properties were found to be superior to the samples prepared by conventional method, due to the rapid processing and uniform temperature distribution, throughout the reaction. The X-ray diffraction (XRD) results confirmed the formation of pure and cubic spinel structure. The crystallite size of the nanoparticles was in the range of 19-25 nm for those prepared by microwave method. The range was higher for the nanoparticles prepared by conventional method. It was evident from the results of energy dispersive X-ray (EDX) analysis that all the samples were pure, with no change in the composition of the elements present. The grain size of the nanoparticles decreases on the addition of Co2+ ions. The high resolution scanning electron microscope (HR-SEM) differentiated the decrease in particle size of the nanoparticles by the two different methods. The UV-visible diffuse reflectance spectroscopy (DRS) was recorded to estimate their band gap energy. The magnetic measurements of all the samples were recorded using vibrating sample magnetometer (VSM) at room temperature in 10 kOe. The values of saturation magnetization (Ms), remanant magnetization (Mr) and coercivity (Hc) were obtained from the magnetic studies. © 2014-2015, Sphinx Knowledge House. All rights reserved.