Abstract Experiments have been performed to further the development of natural fiber reinforced composites as a replacement for glass fiber composites. Untreated and treated surfaces of natural fibers were characterized using FTIR, XPS, and ESEM. Changes in the peaks in the FTIR spectrum at 1730, 1625 and 1239 cm −1 indicated that the alkali treatment removes hemicellulose and lignin from natural fiber surfaces. ESEM indicated the presence of silane on treated hemp and kenaf. XPS shows that hemp has a lower O/C ratio than kenaf. Water absorption experiments were also conducted to determine saturation mass gain. Alkali treated fiber composites absorbed more water than silane treated or untreated composites. The natural fiber composites absorbed more water than the glass fiber composites. Hemp composites, in general, performed worse in flexural testing than kenaf composites.