The effect of synthesis parameters on the metal particle size in final catalysts is reviewed. Several synthesis methods, such as impregnation, deposition precipitation, strong electrostatic adsorption together with stabilization of colloidal and supported metal particles are reported with the main emphasis on the effect of pH in the preparation. In addition to synthesis parameters, also properties of the support, for example point zero charge and specific surface area are of crucial importance. The results revealed that pH and support selection are very important in tuning the metal particle size, moreover aging of the slurry also changes the metal particle size. In addition to preparation the post-synthesis methods, such as washing, calcinations and reduction are shortly reported here. Thermodynamic and kinetic modeling of nanoparticle formation is also summarized here.