The aim of this study is to reveal the mutual influence of the shape and the surface morphology of supported nanoparticles on the reaction kinetics. The analysis has been provided by means of the novel statistical lattice model, which imitates the physicochemical processes that proceed over the supported particles. To simulate the active metal particle the finite Kossel crystal located on the inert support has been chosen. The surface morphology of the particle is defined by distribution of heights of the metal atom columns. The metal atoms attract the nearest neighbour metal atoms and the atoms of the support. The attraction is characterised by interaction energies between the nearest neighbour metal atoms and between the metal atom and the support underneath. The change of morphology is caused by the thermal diffusion of the surface atoms. As a result the equilibrium shape of the particle has been observed to depend on the temperature and the relative ratio of metal–metal and metal–support energies. The model reaction 2A + B₂ → 2AB has been studied, taking into account the roughening of the particle surface and the spillover phenomenon of the adsorbed A_ads over the support. It has been shown that the kinetics of the roughened nanometer-sized particle can be notably different from those corresponding to the flat homogeneous surface. The shape of the nanoparticle can change under the influence of the adsorbed layer even in the absence of the adsorbate–metal interactions.