The chemical and structural properties of kenaf fibers that were treated at different steam pressures during the steam explosion process were investigated. With increased steam pressure, a higher percentage of cellulose and acid-insoluble lignin and a lower content of hemicellulose and pectin were obtained. This result was further confirmed by Fourier transform infrared (FTIR) spectroscopy. X-ray diffraction (XRD) studies revealed that the steam-exploded kenaf fibers were more crystalline than the raw kenaf fibers, and that excessive steam pressure above 3 MPa damaged the cellulose crystalline structure. Scanning electron microscopy (SEM) analysis showed a change in the surface morphology of the treated kenaf fibers. The lower content of gums and the effective defibrillation of steam-exploded kenaf fibers demonstrated the potential of steam explosion treatment in applications of kenaf fibers.