The growth of Cobalt oxides by reactive thermal evaporation of metallic Cobalt in an oxygen atmosphere on a series of oxide substrates, namely SiO 2 , Al 2 O 3 and MgO, has been chemically and morphologically studied by means of XPS and atomic force microscopy (AFM). The XPS results reveal that cobalt oxide grows as CoO (Co 2+ ) for coverages up to some tens of equivalent monolayers on all substrates. For larger coverages, the formation of the spinel oxide Co 3 O 4 has been observed. AFM and XPS quantification allowed us to determine the way of growth of CoO on all substrates, being of Volmer–Weber (i.e. islands) mode for SiO 2 , whereas for Al 2 O 3 and MgO, the growth follows the Frank‐van der Merwe (i.e. layer‐by‐layer) mode. The results are discussed in terms of the mismatch of the lattice parameters of the CoO adsorbates with the substrates. Copyright © 2014 John Wiley & Sons, Ltd.