Abstract: Organic complexant hexamine (hexamethylenetetramine, HMTA) is doped with alkaline earth (AE) metals, and new complexes are designed systematically to explore their nonlinear optical (NLO) properties by carrying out DFT calculations. Optimization of afresh designed geometries has shown their sufficient thermodynamic stability. Moreover, the energy band gap of pure HMTA is 10.62 eV which is reduced up to 2.63 eV for our doped complexes. This shows that alkaline earth metals are effective in enhancing the electronic properties of a system. Time-dependent DFT calculations are achieved, and results show that higher absorption maxima (λmax) along with small transition energies (ΔE) have significantly increased the hyperpolarizability (β0) values (21,338–220,585 au). This higher hyperpolarizability is an elementary prerequisite for improved NLO response of a material. Transition density matrix (TDM) analysis, density of states (DOS) analysis, and electron density difference map (EDDM) studies are executed to get information about electronic distribution, crucial transitions, and electron transfer properties. As a result of these findings, it can be concluded that alkaline earth metal–doped HMTA might be a competitor for NLO materials with remarkable optical and electronic properties and better future applications in the field of optoelectronics.