Good transparent single crystals of Rochelle salt material of potassium sodium tartrate tetrahydrate (PST) was successfully grown by a conventional solution growth technique and an unidirectional growth method of Sankaranarayanan–Ramasamy. The seed crystal obtained by conventional solution growth method was cut along the (100) orientation and subsequently used for unidirectional growth. A large size single crystal was grown by slow cooling technique, with the help of solubility data. The unit cell parameters were determined from single crystal and powder X-ray diffraction studies. FTIR and Raman studies were performed to identify the functional groups present in the title compound. TG/DTA and DSC analyses have also been carried out, and the thermal behaviour of PST crystal has been studied. The grown crystals by both conventional solution growth and SR methods were subjected to various characterization methods such as HRXRD, UV-Vis, hardness, dielectric and Laser damage threshold studies to analyze the properties. The structural perfection of the grown crystals was analysed by high-resolution X-ray diffraction (HRXRD) studies and compared. The laser damage threshold studies were carried out. It is found that SR method grown crystal possesses good optical, mechanical, structural and dielectric properties when compared to conventional solution grown crystal.