The synthesis, growth and structure of a novel organic third order nonlinear optical (NLO) crystal namely, N,N,N′,N′-tetramethylethylenediammonium-bis(4-nitrophenolate) (TMEDA4NP) is presented. The solubility of the compound in methanol and acetonitrile solvents is compared and the growth conditions were optimized. Single crystals of TMEDA4NP were grown in acetonitrile solvent using a slow evaporation technique at 303 K. The crystal structure elucidated from single crystal X-ray diffraction analysis at 293 K showed that the title compound crystallizes in a monoclinic crystal system with space group C2/c. The molecular structure was further confirmed by modern spectroscopic techniques like FT-IR, FT-NMR, UV-Vis-NIR and Fluorescence. The transparency in the visible region and hence the feasibility of the crystal for NLO applications was established from UV-Vis-NIR study. Fluorescence emission of the crystal also revealed that the title compound can serve as a photoactive material. The protonation of TMEDA4NP was unambiguously confirmed from the NMR data. Thermo gravimetric analysis (TGA) showed that TMEDA4NP was thermally stable up to 110 °C. The mechanical strength of the crystal was assessed by a Vickers microhardness tester. Etching studies were carried out on the (100) plane of the as grown surface of the crystal. Third order susceptibility measured using the Z scan technique by employing a picosecond Nd-YAG laser indicates that the title compound can serve as a promising candidate for third order NLO applications.