This study aims to experimentally and numerically investigate the energy absorption of square lattice tubes with uniform and functionally geometrically graded distributions of re-entrant auxetic cells. Three stainless steel 304 specimens were fabricated using a rotary laser cutting machine. These specimens included two auxetic tubes with uniform cell distribution and one with a functionally geometrically graded cell distribution. Quasi-static axial compression tests were conducted on the specimens using a 300 kN universal testing machine. Numerical simulations were performed using Abaqus, and the results were validated against experimental data. The influence of cell angle and cell-wall thickness on the energy absorption capacity of uniformly distributed auxetic tubes was evaluated numerically. Additionally, the energy absorption of square auxetic tubes with three types of functionally geometrically graded auxetic cell distributions was investigated using the finite element method. The evaluation parameters for analysis are energy absorption, specific energy absorption, initial peak force, and crushing force efficiency. The functionally geometrically graded distributions of auxetic cells improved the evaluation parameters relative to uniform cell distributions in lattice tubes. Specifically, the optimally performing graded tube (Gt-Re45t1.0t1.6) exhibited 56% higher energy absorption and 65% higher specific energy absorption compared to the best-performing uniform tube (Ut-Re45t1.4t1.4). Furthermore, its crushing force efficiency was 165% higher, while the initial peak force was 41% lower.