Nonlinear optical single crystals of potassium dihydrogen phosphate doped Congo red dye were grown by slow evaporation method by suitable solvent. The good quality single crystals have been harvested in the period of 23 days. The lattice parameters of the crystal were confirmed by single crystal X-Ray diffraction analysis. The optical transmission observed from the specimen, FTIR confirms the presence of functional groups in the grown crystal. The solidity of the crystal has been studied by Vicker’s micro hardness values. The relative second harmonic generation ability has been tested by Kurtz Perry powder technique. The thermal studies of the crystal has been studied by TGA/DTA analysis.