Interface structures and strain relaxation mechanisms of ferroelectric BaTiO3/SrTiO3 multilayers on (001) MgO substrates were systematically studied by electron microscopy. The multilayers are formed in bilayered structures with different growth morphologies. (i) The lower layer with single crystallinity is an epitaxial layer on the MgO substrate. Defects such as misfit dislocations, anti-phase boundaries, and stacking faults reveal in this layer, acting as a strain relaxation mechanism and (ii) the upper layer is the rest of the multilayer, exhibiting a highly textured columnar structure with small angle boundaries. The columnar grains are formed by local epitaxial growth within individual grains. The strain-relaxation mechanisms are established to understand the growth dynamics of the multilayers. (C) 2013 Elsevier B.V. All rights reserved.