A newly engineered host−guest hydrogen-bonded 2-amino-5-nitropyridinium tetrafluoroborate (2A5NPFB) salt has been designed following a strategy applied to the 2-amino-5-nitropyridinium salts. The crystal structure of organic−inorganic 2A5NPFB has been determined, and it belongs to the noncentrosymmetric space group Fdd2. The powder second-harmonic generation (SHG) efficiency measurement with Nd:YAG laser (1064 nm) radiation shows the highest value among 2-amino-5-nitropyridinium derivatives with the phase-matching property. The optical transparency window in the visible and near-IR (420−1100 nm) regions was found to be good for nonlinear optical applications. The experimental conditions of the synthesis and its spectral analysis, namely FT-NMR, FT-IR, and FT-Raman, have also been studied. Thermal stability of 2A5NPFB and its tendency to grow as single crystals in solution have been identified.