The morphological and physical properties of poly(lactic acid) composites reinforced by woven hemp fabrics pre-treated with enzyme and ammonia were investigated in this study. During the preparation procedure of the poly(lactic acid)/hemp composites, enzyme and ammonia treatments were applied to the surface of woven hemp fabrics in order to improve the interfacial adhesion between hemp fibers and poly(lactic acid) resin. The mechanical and morphological properties of poly(lactic acid)/hemp composites were examined via Instron measurement and scanning electron microscopic observation. Furthermore, the thermal shrinkage and flame-retardant properties of the composites were analyzed to understand the effect of the pre-treatment.