An organic adduct nonlinear optical material m-nitrobenzoic acid⋅diethanolamina (C11H16N2O6) has been characterized by X-ray powder diffraction. Experimental values of 2θ corrected for systematic errors, relative peak intensities, values of d, and the Miller indices of 56 observed reflections are reported. The powder diffraction data have been evaluated, and the figure of merit was found to be F30=57.9 (0.0108, 48). The unit cell parameters were refined by a least-squares fit with a Cc space group and a=22.973(5) Å, b=4.6657(6) Å, c=15.023(3) Å, β =124.45(1)°, V=1327.75 Å3; Z=4, Dx=1.37 g/cm3. The powder diffraction results are in agreement with those obtained from single crystal structure data.