Pure L Threonine and Methyl Violet doped L Threonine single crystals were grown by slow evaporation technique. The grown crystals were characterized using PXRD, UV-Visible, FTIR and NLO spectroscopies. PXRD data were collected and indexed. Grain size, microstrain and dislocation density were calculated. FTIR data provides the functional group of all the grown crystals. UV-Visible absorption spectra were recorded and the optical bandgap energy and the refractive index of the grown crystals were also determined. Grown crystals grown are violet in colour, transparent and needle shaped. They belong to the face centered orthorhombic crystal system. The optical band gap energies of all the grown crystals are almost constant. UV-Visible spectrum shows the full absorption and transmission in the entire visible region. So, the pure and Methyl Violet doped L Threonine crystals are very good material for optoelectronic applications. NLO study shows that due to the presence of the dopant dye, L Threonine has lost its SHG efficiency. Hence it can be used as semiconductors, superconductors, photonic crystals etc.