Starch-based foamed blocks reinforced with natural fillers and with a high potential for being applied as bioderived and biodegradable shaped protective packaging were produced in this work. The use of natural fillers as reinforcement in biopolymers represents a successful strategy widely employed mainly due to their chemical compatibility. Nevertheless, their effect in the mechanical properties of foamed biopolymers such as starch is still uncertain because they not only affect the properties of the solid polymer matrix within the cell walls and struts but also the main mechanisms comprising a foaming process such as nucleation, expansion and stabilization of the cellular structure. Moreover, the homogeneities of the cellular structures obtained are usually poor which complicates even more the analyses. This work aims at providing more insight in the relation cellular structure-mechanical properties in starch-based polymer foams reinforced with natural fillers by characterizing their cellular structure in detail and relating them with their mechanical properties measured in compression. In addition, these starch-based foams were produced by a foaming process consisting on the interaction of microwaves with the polymer matrix, which is especially interesting when water acts as the blowing agent as in this work. The loose of water during the foaming process make the properties of the polymer within the cells walls and struts evolve, which leads to obtain brittle foams from highly flexible solid precursors