Magnetite (Fe3O4) thin films are synthesized by chemical vapor deposition (CVD) with the cyclohexadiene iron tricarbonyl Fe(C6H8)(CO)3 liquid precursor. The growth of pure, polycrystalline, and stoichiometric Fe3O4 films is confirmed by X-ray diffraction, Raman spectroscopy, time-of-flight secondary ion mass spectrometry, and conversion electron Mössbauer spectroscopy. At 297 K, the resistivity for 24.8 nm (100 nm) Fe3O4 thin film is 17 × 10−3 Ω cm (4.2 × 10−3 Ωcm), indicating the good electrical quality of the as-deposited layers. Magnetoresistance (MR) up to −2.2% is measured at 297 K at 1.1 T, corresponding to 15% electron spin polarization. A gradual increase of MR is observed at low temperature. In particular, the observed MR = −4.4% at 120 K (at 0.8 T) is attributed to an intrinsic enhancement of the electrons spin polarization up to 21.5%.