Natural cellulosic fibers, including hemp, are increasingly being used for composite reinforcement. However, their poor adhesion with synthetic resins limits their use as reinforcing agent. It is generally accepted that interfacial adhesion can be best described in terms of dispersion forces and acid-base interactions. Therefore, there is a need for quantitative determination of acid-base character of natural cellulosic fibers. In this study, acid-base characteristics and dispersion component of surface energy of hemp fibers have been determined using inverse gas chromatography. Effect of alkalization and acetylation on acid-base characteristics has also been examined. The results indicate that alkalization and acetylation make the hemp fiber amphoteric, thereby improving their potential to interact with both acidic and basic resins. Finally, a parallel is drawn between the changes in fiber-matrix acid-base interactions and the actual improvement in the mechanical properties of the composites manufactured using resin transfer molding process.