A novel l-arginine salt nonlinear optical single crystal, l-arginine p-nitrobenzoate monohydrate (LANB) has been grown by slow cooling method from aqueous solution. Its solubility at different temperatures in water was measured. The grown crystal was characterized by the elemental analyses, X-ray single crystal and powder diffractions, Fourier transform infrared and Raman spectra. The structure analysis revealed that LANB belongs to the monoclinic crystallographic system, space group P2 1 , with unit cell parameters: a=8.566(3), b=5.817(2), c=17.131(7)Å, β=101.223(5)°, Z=2 and V=837.2(6)Å 3 . The proton and carbon configurations of l-arginine were confirmed through 1 H NMR and 13 C NMR spectra analyses. The linear and nonlinear optical properties of LANB crystal were studied by the use of transmission spectrum and second harmonic generation (SHG). The thermal properties were investigated by using thermo gravimetric (TG) and differential thermal analysis (DTA).