The quality 2-amino-5-chloropyridinium 4-aminobenzoate (2A5ClP4AB) single crystals were grown in methanol solvent by employing the solvent evaporation technique. The stoichiometry ratio of 2A5ClP4AB was confirmed by microanalysis. The melting point, decomposition, crystalline phase, purity, and specific heat capacity of 2A5ClP4AB crystal were explored by thermogravimetric-differential thermal analyses (TG–DTA), differential scanning calorimetry (DSC), and modulated scanning calorimetry (MDSC) methods. The various dielectric properties of 2A5ClP4AB single crystal concerning temperature and frequency were examined by dielectric measurements. The nonlinear optical (NLO) parameters such as dipole moment, polarizability, first-order hyperpolarizability, and second-order hyperpolarizabilities of the 2A5ClP4AB molecule were computed using density functional theory (DFT) by utilizing the Gaussian 09 program. The figured HOMO–LUMO energies of 2A5ClP4AB demonstrate the occurrence of a charge transfer mechanism, whereas the MESP map illustrates how various molecular interactions took place in it. Hirshfeld surface analyses helped to decode the nature of the interactions and packing structure of the crystals. The above studies were intended to explore the structural, thermal, electrical and NLO properties of 2A5ClP4AB and also to strengthen its effectiveness for optoelectronic and frequency conversion applications.