Performance of a mechanical buffer can be significantly improved by strengthening the materials and optimizing its structure. Manufacturing of high-strength and light-weight foam-filled tubes (FFTs) has been proved to be an ingenious strategy. In this work, the in situ grown carbon nanotubes (CNTs) were used to reinforce aluminum (Al) foams. The FFTs were prepared by inserting CNT/Al composite foams (CFs) into 6061 Al alloy empty tubes (ETs). The crushing behavior and energy absorption property of the as-prepared CNT/Al FFTs (C-FFTs) were evaluated using uniaxial compressive tests. The results show that the adopted CFs can effectively interact with outside tubes in C-FFTs. The C-FFTs significantly improve the compressive performance and energy absorption property, but only slightly increase the structure weight compared to single ETs. The plateau stress and energy absorption capacity of C-FFTs are nearly 3.5 and 3.7 times higher than those of ETs, respectively. This phenomenon is ascribed to the stable support of CFs and the excellent load transfer ability of CNTs.