Two ferulic acid derivatives (BDF and BDF-Me) were prepared using chemoenzymatic synthesis and used as additives for the pretreatment of hemp fibers. Incorporation of these fibers into a polycaprolactone matrix by hot-melt extrusion process aimed to improve the dispersion of the fibers and the mechanical properties of the resulting materials. Youngs modulus and tensile strength of the composites were investigated at the micrometer scale by chemical imaging. The very simple methylation of the phenolic functions led to significant mechanical properties differences due to the dispersion of the fibers caused by a plasticizing effect of the ferulic acid derivative. This significant plasticizing effect of BDF-Me is observed at a content as low as 0.8 w% and opens the way for synthesizing a new family of biobased plasticizers involving transition from crystal state to amorphous phase.