L10order was optimized in FePd epitaxial thin films prepared using dc magnetron sputter deposition on MgO(001) substrates by investigating various growth temperatures. A series of films was grown at the optimal temperature with varying thickness and degree of chemical order to investigate the interplay between the microstructure, magnetic anisotropy, and magnetic domain structure. The experimentally measured magnetic domain size/period and magnetic anisotropy in this high perpendicular anisotropy system were found to be correlated following the analytical energy model proposed by Kooy and Enz that considers a delicate balance between the domain wall energy and the demagnetizing stray field energy.