The development of sustainable rubber compounds is gaining traction due to the environmental issues caused by the extensive use of polymers and the need to move towards a circular economy. However, the conventional fillers used in elastomer compounds to improve their mechanical performance hinder their degradation. Therefore, materials such as chitin, chitosan, lignin, and cellulose, are being considered as sustainable fillers in elastomeric compounds. This chapter presents a review that addresses the promising biodegradable fillers from vegetable sources, their biosynthesis, chemical properties, applications, reinforcing effect, and the improvements in the performance of composite materials based on natural and synthetic rubber matrices. This review also provides brief information on recently identified bacterial and fungal strains for the degradation of both polymer and fillers.