Organic single crystals of new stilbazolium derivative, (E)-4-(3-ethoxy-2-hydroxystyryl)-1-methyl pyridinium iodide (3ETSI), was grown by slow evaporation technique. Single crystal X-ray diffraction study revealed that 3ETSI crystallizes in monoclinic crystal system with centrosymmetric space group P21/c. The characteristic functional groups of the grown crystal were identified by FT-IR spectral studies. The 1H NMR spectral studies further confirm the molecular structure of the grown crystal. The thermal behaviour of 3ETSI crystal was studied by TG/DSC analysis. The grown crystal was found to be transparent in the region between 471 and 800 nm as indicated by the UV–visible spectral studies. Photoluminescence spectrum of 3ETSI crystal shows broad green emission peak at 529 nm. The mechanical strength of the grown crystal was estimated by Vickers microhardness tester. The laser damage threshold of 3ETSI crystal was found to be 2.5 GW/cm2 using Nd: YAG laser (1064 nm). Etching studies enunciate the two-dimensional (2D) layer growth mechanisms in the grown crystal. The third-order nonlinear optical properties including nonlinear refractive index (n2), nonlinear absorption coefficient (β), and third-order nonlinear optical susceptibility (χ(3)) of 3ETSI crystal were investigated by the Z-scan technique using continuous wave (CW) He-Ne laser at 632.8 nm. © 2017, Springer Science+Business Media New York.