• The present molecular complex is crystallized in the space group of P2 1 2 1 2 1 . • The emission peak observed at 415 nm in PL spectrum indicates blue emission. • The SHG efficiency of the present crystal is 1.6 times higher than that of KDP. • The present crystal is thermally stable upto 224°C. • Hirshfeld surface analysis illustrates that O•••H interactions are more prominent. The single crystal of 3-hydroxy pyridinium 2-hydroxy benzoate (3HP2HB) molecular complex was grown by solution growth method. The conformation of crystal structure was done by single crystal X-ray diffraction (SCXRD) technique and it uncovers that the title crystal belongs to orthorhombic crystal system with P2 1 2 1 2 1 space group. The absorption spectrum of grown crystal was recorded using UV–Vis spectroscopy. Fluorescence emission spectrum was observed in the blue band region using spectroflurometer. 1 H and 13 C NMR spectral technique was used to predict the presence of hydrogen and carbon bonded network. The Fourier transform infrared spectral technique (FT-IR) was used to identify the presence of various functional groups in the crystal structure. The second order nonlinear optical property of the crystal was studied by the modify Kurtz-Perry powder SHG technique using Nd:YAG laser with wavelength 1064 nm. The thermal stability of the title crystal was carried out by TG/DTA studies. The presence of inter-molecular interactions was examined by Hirshfeld surface. The DFT method was used with B3LYP/6-311++G(d,p) basis set to compute the structural, electronic and reactivity properties of the title crystal.