Epitaxial Fe3O4 thin films were grown on TiN buffered Si(001), Si(110), and Si(111) substrates by dc reactive sputtering deposition. Both Fe3O4 films and TiN buffer are fully epitaxial when grown at substrate temperatures above 150 °C, with textured single phase Fe3O4 resulting from room temperature growth. The initial sputtered Fe3O4 formed nuclei islands and then coalesced to epitaxial columnar grains with increasing film thickness. The magnetization decreases and the coercive field increases with decreasing film thickness. There is no in-plane magnetic anisotropy of epitaxial Fe3O4(001) on Si(001) but Fe3O4 films grown on Si(110) and Si(111) substrates show uniaxial in-plane magnetic anisotropy.