Density functional theory (DFT) in its B3LYP implementation is used to investigate the reaction of ammonia with the late (Co+, Ni+, and Cu+) first-row transition metal cations in both high- and low-spin states. The potential energy surfaces (PES's) leading to three different exit channels are closely examined. The binding energies for the reaction products are calculated and compared with the corresponding experimental values. A comparison with our earlier works covering the reactivity of the Sc-Fe series of cations is made in order to underline similarities and differences of the reaction mechanisms as well as to establish trends along the row.