The hard-shelled seed industry plays an important role in the global agricultural economy. As a result of nut industrialization, considerable amounts of by-products and residues are produced year by year, burnt as fuel or discarded as non-valued waste, by-passing a potential source of valuable compounds or features. Over the last decade nutshells have received great interest due to their lignin concentration and their antioxidant, physical and mechanical features. It was found that these properties vary among cultivars, latitude and localities of plantation. On the other hand, there is inconsistences regarding to mechanical and some biochemical properties of both nutshells, which aimed to explore the status of potential hazelnut and walnut shells appli-cations into sustainable circular bio-economy chains. Hence, this review deals with the recent scientific literature on their chemical composition as well as their functional applications as an approach to sustain the utilization of the main by-product derived from the nut-industry.