Sandwich structures are widely used for many different applications since they offer exceptional benefits, providing a high bending stiffness with a very low weight. In aeronautics, sandwich panels are commonly made of Nomex honeycomb, and therefore this core has been studied for decades. Concerning the literature, most of the investigations on honeycomb cores are focused on to investigate the compression properties of the structure, for energy absorption applications or impacts on sandwich panels. In the other hand, there are far fewer studies concerning the understanding of the shear nonlinear behavior of the honeycomb [1], this can be considered a major drawback, knowing that it’s the core who absorbs most of the shear components when a bending force is applied. To help fill this gap, this work focuses on to study the shear behavior of the honeycomb structure. Several experimental tests are conducted using different boundary conditions to observe the buckling of the cells. This helps to understand the causes of the phenomenological stages that appear when the honeycomb structure is submitted to shear loads. Finally, a numerical approach is used to simulate the honeycomb response to be able to see on the interior cell walls and to better understand this phenomenon. This work is a contribution to the understanding of the shear buckling of Nomex honeycomb cores.