The organic nonlinear optical crystals of pure benzilic acid (PBA) and tartaric acid doped benzilic acid (TADBA) single crystals were grown by using slow evaporation method utilizing dimethyl formamide (DMF) as a solvent. Transparent single crystals of PBA and TADBA of dimensions 9 x 4 x 1 mm(3) and 7 x 5 x 2 mm(3) were grown after thirty days. Lattice parameters and space groups of PBA and TADBA were evaluated using single crystal X-ray diffraction analysis. Employing Fourier transform infrared spectral analysis, various functional groups in pure and doped crystals were ascertained. H-1 and C-13 nuclear magnetic resonance spectral analysis suggests the presence of hydrogen- and carbon-bonded network. Optical transparency of PBA and TADBA was investigated using ultraviolet-visible (UV-vis) spectral analysis whereas thermal properties of the grown crystals were studied by thermogravimetric and differential scanning calorimetry analyses. Second harmonic generation efficiency of PBA and TADBA was found to be 2.2 and 2.7 times higher than that of potassium dihydrogen phosphate. (C) 2016 Elsevier B.V. All rights reserved.