One-dimensional α-MoO3 nanofibers of 280–320 nm diameters were synthesized by a hydrothermal method. The morphologies and compositions of as-synthesized α-MoO3 nanofibers have been characterized by X-ray powder diffraction, Raman spectroscopy, and field-emission scanning electron microscopy. X-ray photoelectron spectroscopy showed the predominantly 6+ oxidation state with a small percentage of reduced δ+ (5 < δ < 6) oxidation state. The field-emission properties of α-MoO3 nanofibers show a lower turn-on electric field of 2.48 V µm -1 and threshold electric field of 3.10 V µm -1 . The results suggest that the α-MoO3 nanofibers are promising candidate for efficient and high-performance field-emission devices.