The interest in using natural fibers in composites has increased in recent years due their lightweight, non-abrasive, combustible, non-toxic, low cost and biodegradable properties. However, lack of good interfacial adhesion, low melting point and poor resistance to moisture absorption make the use of natural fiber reinforced composites less attractive. Chemical treatment of the fiber can clean the fiber surface, chemically modify the surface, stop the moisture absorption process and increase the surface roughness. In this study, kenaf bast fibers, supplied by MARDI, for use in fiber-reinforced composites, were modified using NaOH of different concentrations. Morphological and structural changes of the fibers were investigated using scanning electron microscopy (SEM). A series of fiber bundle tensile tests were also performed to evaluate the effect of the treatments on the fiber tensile strength. It has been found that the alkalization treatment has improved the mechanical properties of the kenaf fiber significantly as compared to untreated kenaf fiber. It is also interesting to note that 6% NaOH yields the optimum concentration of NaOH for the chemical treatment.