The design of interfaces in green polymer composites is a crucial factor in ensuring mechanical strength in composite materials. While cellulose fibers have high intrinsic mechanical strength, their reinforcing effect in polymer composite materials highly relies on the creation of a tight interface with the surrounding polymer matrix. In parallel, the hydrophilicity of the cellulose has to be compatibilized with often more hydrophobic polymer matrixes. In this study, the cellulose interface has been modified by the self-assembly of polymer-peptide nanoparticles regulating the adhesive strength in the interface. The incorporation of catecholic groups allows physical adsorption at the cellulose surface in parallel with the mimicking of mussel-inspired adhesion in presence of dopamine groups. In this study, the cellulose surface modification has been performed with different concentrations of the adhesive nanoparticles, observing interesting trends in adhesive forces at either the nano- or macroscale length. The nanoscale adhesion has been tested with atomic force microscopy, showing the influence of nanoparticle deposits either as a monolayer or multilayer onto the cellulose surface. The macroscale adhesion was characterized by single-fiber pull out tests indicating an optimum concentration of nanoparticles at the surface to provide high adhesive interface strength. In addition, the nanoparticles show colorimetric and fluorescent response to mechanical shear stresses providing an evaluation tool to explore the interface phenomena upon failure.