Magnetorheological (MR) gels are a class of smart materials whose mechanical characteristics can be modified by the application of an external magnetic field. This paper aims at the investigation of the effect of the size of spherically shaped particles on the magnetorheological gels and the significance of its influence on the properties of the MR gels. MR gels are prepared using magnetite (Fe3O4) nanoparticles and/or carbonyl iron (CI) microparticles dispersed in a polymer gel. A free decay test apparatus built in-house is used to obtain the magnetic field dependent shear response of the gels under dynamic conditions at room temperature and the results are compared for varying sizes of particles. The results indicate a clear trend of increase in storage modulus of the magnetic gel with the decrease in the size of the particles under same conditions of magnetic field and mass fraction. For example, the increase in the shear storage moduli of the magnetic gel, prepared with a mass fraction of 20% of carbonyl iron particles of sizes 3.4 μm and 1.4 μm increase by 16.3% and 18% respectively of the zero field moduli, while the gel with the same mass fraction of magnetite nanoparticles increases to 28%. © 2019 Elsevier B.V.