Epitaxial MgFe2O4 thin films of different morphologies were prepared by solid state reactions between MgO(100) substrates and iron oxide vapor. The formation of MgFe2O4 proceeds via cation counterdiffusion in the fixed oxygen sublattice. Depending on the substrate temperature used, epitaxial spinel films of different composition and magnetic properties were obtained. Crystal structure, composition and submicron morphology were investigated by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), energy dispersive X-ray spectroscopy (EDX), transmission (TEM) and high resolution (HREM) electron microscopy and selected area electron diffraction (SAED). Magnetic hysteresis loops were recorded at room temperature using the magneto-optical Faraday effect.