A theoretical study of the different AlC2N isomers has been carried out. The global minimum is predicted to be a linear AlCCN isomer, whereas the previously predicted ground state, a three-membered ring isomer: lies much higher in energy (more than 25 kcal/mol at the more reliable levels of theory). We have found four other structures lying lower in energy than the three-membered ring, two of them being rhombic structures. The preferred atomic arrangement for linear geometries, as in the case of its analogue BC2N system, is AlCCN. However, contrary to what is observed for BC2N, the global minimum is a (3)Sigma state. Predictions for the vibrational frequencies, rotational constant, and dipole moment, as well as for the atomization energy and dissociation into Al + CCN, have been made for the global minimum. On the basis of these results we may conclude that the ground state of AlC2N is relatively stable and therefore it might be of interest for experimentalists.