New semiorganic nonlinear optical (NLO) Potassium Boro-oxalate single crystals have been grown by Slow Evaporation technique at ambient temperature. The title compound has been subjected to single-crystal X-ray diffraction analysis to identify the unit cell parameters. Fourier Transform Infrared spectroscopic analysis was carried out on the grown sample to ascertain the fundamental functional groups. Optical absorption studies illustrate low absorption in the entire UV and Visible region. The crystal was subjected to TGA DTA analysis to find its thermal stability. The dielectric response of the crystal with varying frequencies was studied. The mechanical property of the grown crystals had been analyzed by Vickers’s microhardness method. The NLO property of the grown crystal has been confirmed by the Kurtz powder Second Harmonic Generation (SHG) test.