The density functional theory computations were performed in order to investigate the impact of Cd-decoration upon the capability of an AlN nanotube (AlN-NT) in in detecting chloropicrin (CP). The interaction between the pure AlN-NT and CP was weak, with a sensing response (SR) of around 6.9. After the Cd atom was decorated onto the surface of AlN-NT, an increase was observed in the adsorption energy of CP from −6.0 to –22.4 kcal/mol. Following the Cd-decoration, a substantial rise was also observed in the SR to 82.5. The recovery time (RT) when CP was desorbed from the surface of Cd@AlN-NT at 298 K was 21.0 s. This suggested the possibility of using Cd@AlN-NT as a suitable CP sensor with high sensitiveness and a short RT. It was demonstrated that the Cd@AlN-NT was capable of selectively detecting CP among HCN, toluene, acetone, ethanol, and formaldehyde vapors.