The magnetic anisotropy of epitaxial spinel ferrite CoFe2O4 films grown on SrTiO3 substrates by pulsed laser deposition can be reoriented by inserting a thin SrRuO3 buffer layer. Without SrRuO3, the CoFe2O4 films show a uniaxial anisotropy with the easy axis perpendicular to the film plane, while inserting a SrRuO3 buffer layer results in the switching of the easy axis into the in-plane orientation. This is associated with a tensile and a compressive strain for the films without and with buffer layer, respectively, which is also correlated with the different density of interfacial misfit dislocations. As a result, the ferrite films can be effectively tailored by using SrRuO3.