Good-quality organic nonlinear single crystal of 2,3-dimethyl-N-[(E)-2,4,5-trimethoxy benzylidene] aniline (DTA) was synthesized and successfully grown at room temperature by adapting slow evaporation technique using mixed solvent of acetone and methanol. The crystal structure was experimentally confirmed by single-crystal X-ray diffraction, where the DTA crystals crystallize in the centric space group (P1 ¯ ) with triclinic crystal system. The surface morphology of DTA was examined by the Field Emission Scanning Electron Microscope (FE-SEM) technique. The presence of various modes of functional groups of the title crystal was analyzed by Fourier-Transform Infra-Red (FT-IR) spectra. Ultraviolet–Visible-Near Infrared (UV–Vis–NIR) spectrum showed high optical transparency of 88% in the Vis and NIR region with a UV–Vis absorption edge of 390 nm. The result of photoluminescence studies suggests that the DTA crystal can be used as source material to exhibit green emission light. From thermogravimetric-differential scanning calorimetry (TG-DSC) analysis, the melting point of the grown crystal was found to be 111 °C. The standard Z-Scan technique was employed to evaluate the third-order nonlinear optical properties of the DTA crystal. The obtained third-order nonlinear parameters were compared with few of the already reported NLO crystals. All these findings indicate that the title crystal may be an attractive material for nonlinear optical device applications. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.