Conventional plastics can be substituted for protein-based bioplastics due to their natural origin and their biodegradability. Nevertheless, their properties are inferior to those obtained for synthetic plastics. The chemical crosslinking of these bioplastics with aldehydes could improve their properties to compete in the actual market. Thus, the main goal of this article was to assess the influence of the incorporation of aldehydes with different aliphatic chain length on the physicochemical (crosslinking degree, colour and transparency), mechanical (flexural and tensile behaviour) and functional (water uptake capacity and biodegradability) properties of protein-based bioplastics. In this sense, pea protein, a by-product of food industry, was used as raw material, processing it by injection moulding to obtain the bioplastics. Formaldehyde, glyoxal and glutaraldehyde were the aldehydes used as crosslinking agents. The results show the rise of the mechanical properties with the incorporation of the aldehydes, depending on the degree of crosslinking they generate. All this also causes a consequent loss of the water uptake capacity and an increase in biodegradability time. In conclusion, this work opens a new alternative to develop sustainable bioplastics that can be used in the market.