We report the surface-mediated polymerization of FtsZ protein, the prokaryote homologue of tubulin, by AFM. FtsZ protein can form filaments on mica whereas the bulk FtsZ concentration is orders of magnitude lower than the critical concentration. Surface polymerization is favored by a local increase in protein concentration and requires a high mobility of proteins on the surface. To generalize to other cytoskeleton protein, we also show that mica can initiate the formation of tubulin protofilaments. This study is of particular interest for studying cytoskeletal protein dynamics by AFM but also for the surface autoassembly of nanostructures.