The effect of alkali metals (Li, Na and K) interaction on the nonlinear optical response (NLO) of Ga12N12 nanocage has been performed using density functional theory (DFT) calculations. The results show that the [email protected]12N12 structures are energetically favorable with negative interaction energies in the range of ‒1.50 to ‒2.28 eV. The electronic properties of decorated structures are strongly sensitive to interaction with the alkali metals. The HOMO-LUMO gap of Ga12N12 is reduced by about 70% due to the decoration with alkali metals. It is obtained that the adsorption of alkali metals over the tetragonal ring of Ga12N12 nanocage remarkably enhances the first hyperpolarizability up to 6.5×104 au. The results display that decorating Ga12N12 nanocage with alkali metals can be introduced it as a novel inorganic nanomaterial with significant NLO properties.