Ferroelectric domains were investigated using piezoresponse force microscopy in superlattices composed of multiferroic BiFeO3 and SrTiO3 layers. Compared to single BiFeO3 thin films, a reduction in the domains size and a suppression of the in-plane orientation of domains are observed in a superlattice of (BiFeO3)4 (SrTiO3)8, suggesting a constrained ferroelectric domain orientation along the out-of-plane 〈 001 〉 direction. Such modification of domain size and orientation in BiFeO3 -based heterostructures could play a vital role on engineering the domains and domain wall mediated functional properties necessary for device applications. © 2010 American Institute of Physics.