The development of biodegradable and recyclable bio(nano)composites based on renewable resources can contribute to mitigating the effects of plastic pollution and the depletion of fossil fuels. In this frame, thermoplastic biodegradable polyesters blended with lignocellulosic derivatives are of interest. Reactive melt processing is a sustainable and scalable strategy to tackle the drawbacks of poor lignocellulose dispersion and adhesion with the polymer matrix. Reactive melt processing combines melt compounding with chemical reactions, and it has been explored to tune the interface of bio(nano)composites, improve their performance and add new functionalities. Different categories of interface design have been investigated, including the modification of the polymer matrix, of the lignocellulose, the addition of a third component, and in-situ polymerization. Peroxide-initiated branching/crosslinking carried out in synergy with the water-assisted feeding of lignocelluloses enabled the formation of a uniform hybrid polymer/lignocellulose network that provided creep resistance and shape memory properties. Grafting of bio-sourced oils onto industrial lignin was explored to plasticize lignin and favour its miscibility with polyesters. In-situ polymerization of bio-sourced ethylene brassylate to graft the polymer from the cellulose surface resulted in an effective method for (nano)cellulose dispersion and stress-transfer with the matrix.Amphiphilic copolymers were designed as third components to mediate the interface between cellulose nanofibrils and the polyesters, enabling their dispersion, increasing stiffness and strength, while preserving the deformation of the biocomposites.A deeper understanding of bio(nano) composites’ interfaces proposes sustainable alternatives for the industrial replacement of conventional plastics and paves the path for future investigations.