The goal of the work was to recycle waste paper, utilize it as a filler and investigate the properties of the obtained recycled polypropylene-based composite. Crystalline cellulose from the waste paper was regenerated in accordance with the developed method in acid medium under mild conditions. The morphology, crystallinity degree, shape, and sizes of the obtained cellulose particles were characterized. It was found that the extracted crystalline cellulose contained more amorphous regions than the kraft pulp, and was characterized by a more hydrophilic structure. The extracted crystalline cellulose microparticles were used as a biofiller in the recycled polypropylene-based composite in its binary and ternary formulations, incorporating maleic anhydride-grafted polypropylene as an adhesion enhancer. The binary composite was characterized by unsatisfactory mechanical and wetting properties. The presence of the adhesion enhancer in the composite's formulation improved the mechanical properties, increased the hydrophobicity and thermal stability of the composite.