Growth of organometalic nonlinear optical (NLO) L – proline strontium bromide tetrahydrate (LPSBT) single crystals were reported for the first time by slow evaporation technique. Crystal structure was elucidated by single crystal X – ray diffraction analysis. Fourier transform infrared and FT – Raman spectroscopic studies were performed to identify the various functional groups present in the grown crystal. Optical transmittance of the grown crystal was investigated by UV–Vis–NIR spectral studies. The lower cut off wavelength of the grown crystal is observed at 240 nm. The photoluminescence spectral study of the grown crystal showed an emission peak at 410 nm. Mechanical strength was assessed by Vickers microhardness measurements. The dielectric constant and dielectric loss were studied as a function of frequency at various temperatures. Thermal stability of the grown crystals was studied by thermogravimetric analysis, differential thermal analysis and differential scanning calorimetry. The laser induced surface damage threshold for the grown crystal was determined using Nd:YAG laser. The Kurtz powder second harmonic generation efficiency of grown LPSBT is about 0.8 times that of potassium dihydrogen orthophosphate.