The benefit of using a combination of alkali pre-treatment and ball milling in processing hardwood particles into biocomposites via equal channel angular pressing (ECAP) was demonstrated. The penetration of bonding additives (polyethyleneimine and tannic acid) into hardwood structures was enhanced by the pre-treatment, resulting in plasticization and cross-linking derived from the additives during the particle processing. A significant improvement in the biocomposites’ mechanical properties was obtained, reaching flexural strength of 28–29 MPa and flexural modulus of 3650 MPa, comparable to those displayed by commercial wood fiberboard using thermosetting resins as the binding agent. This adds to the promise of developing biocomposites from industrial or agricultural waste through the simple and efficient ECAP technology in conjunction with common pre-treatment methodologies for wood particles.