<p>The 3D auxetic structures are increasingly recognized for their potential to enhance specific energy absorption (SEA). Conventional auxetic structures are typically limited to 2D or 2.5D configurations and inherent gaps are generated between the unit cells due to the length of the connecting nodes. There is a need for research focused on improving the specific energy absorption through effective 3D deformation behaviors. This study proposes a novel 3D auxetic octahedron structure designed to control the cell unit structure and enhanced SEA by adjusting the compression ratio. Numerical analysis was conducted to evaluate the deformation behavior and verify the negative Poisson’s ratio of the designed structures. To validate the mechanical properties, specimens were fabricated using additive manufacturing, and compressive tests were performed to analyze the stress–strain curves relative to the structural parameters. Furthermore, the performance of the auxetic structure was rigorously benchmarked against stiffness dominated FCC and bending dominated BCC lattices. The results demonstrate that the proposed 3D auxetic octahedron structures exhibit stiffness comparable to that of the FCC structure while providing a more ductile response and enhanced specific energy absorption. These findings indicate that the developed expanded octahedral geometries offer significant advantages for industries requiring superior impact shock absorption and provide a versatile design strategy for future auxetic research.</p>