In this paper, free convection of ferrofluid in a cavity heated from below in presence of external magnetic field is studied numerically using the lattice Boltzmann method. The enclosure is filled with a mixture of kerosene-cobalt. This investigation was compared with other experimental and numerical works and found to be in excellent agreement. Effects of Rayleigh number, magnetic coefficient, heat source length and volume fraction of cobalt on flow and heat transfer characteristics are examined. Results show that particles with a smaller size have better ability to dissipate heat, and a larger volume fraction would provide a stronger driving force which leads to increase in temperature profile. The Nusselt number has direct relationship with the Rayleigh number and heat source length while it has reverse relationship with size of nanopartide and volume fraction of cobalt. (C) 2014 Elsevier B.V. All rights reserved.