Auxetic structures possessing a negative Poisson’s ratio present a very interesting research subject because of their extraordinary mechanical responses. These weird materials are progressively utilized across the industry because of their superior mechanical properties like the higher stiffness, strength, hardness, and energy absorption. This scientific paper denotes an experimental study of the indentation behavior of a composite sandwich with auxetic honeycomb core structure. A biological material made from renewable resources was used to make the specimens. It consists of a tape of polylactic-acid reinforced with flax fibers. The sandwich composites were manufactured utilizing 3D printing technique. Different core height was tested in order to depict the cell wall lengths effect. The results present the core height effect on the indentation comportment and the energy absorption capacity. Throughout the indentation tests, the auxetic cells of the core material misshape elastically and cave in under high loading. The cells in contact with the indenter cave in while forming folds on the cell walls. The total crushing of the cell walls indicates the begin of the densification phase. Results show that the cell wall length play an important role on the mechanical behavior. The energy absorption capacity is higher for sandwich with the longest cell wall lengths.