The mandatory heat input supplied during the welding makes the weld zone weaker by grain growth, wider heat affected zone (HAZ), reduction in yield and tensile strengths, and distortion. Therefore, cryogenic cooling is applied for the improvement of the microstructure, mechanical properties, and dimensional accuracy. In this research thin austenitic stainless-steel sheet of grade 316 was welded by key-hole mode plasma arc welding in a single pass without using filler but with and without cryogenic cooling media. The microstructures, microhardness, and tensile properties at room temperature of cryogenically and conventionally cooled weld samples were analyzed and compared. The microstructural behavior of samples was characterized by metallurgical microscopy and scanning electron microscopy. The SEM Analysis reveals γ austenite and δ ferrite phases in conventionally welded test samples. M23C6 is formed in small amounts from δ ferrite, surrounding the δ ferrite on grain boundaries. In cryogenic cooled samples, delta ferrite is detected on grain boundaries of the austenitic matrix. Moreover, traces of (Cr, Fe)2N are also revealed in certain cryogenic cooled samples due to liquid nitrogen impingement. In gel cooled samples, M23C6 is shown due to comparatively prolonged duration of cooling and the results reveal that the liquid nitrogen and thermos gel improved average grain size up to 83.53 % and 66.84% respectively as compared to an average grain size of conventional plasma weld. The reduction in HAZ is observed to be about 43.38% and 7.92% for liquid nitrogen cooled and thermo gel samples respectively as compared to conventional weld. Moreover, the tensile and yield strength of liquid nitrogen-cooled weldments increased up to 22.28% and 28.96% respectively while for gel-cooled welded sample, a 10.50% improvement in tensile strength and 3.10% in yield strength was observed. Furthermore, the reduction of 75% in distortion is achieved for welded samples with liquid nitrogen cooling.