Fiber laser welding experiments are conducted on SS316L austenitic stainless steel plates based on the statistical design of experiments technique. A special kind of fixture is designed and fabricated with a facility to provide argon gas and is made up for bead protection. The influence of beam power, welding speed, and defocused position on fusion zone width, fusion zone area, and tensile strength of weldments is studied and discussed briefly. The most influencing factors and their percentage contribution on output responses are identified by analysis of variance technique. Beam power directly influences the bead features, whereas welding speed inversely affects it. However, the defocused position shows an insignificant effect on the fusion zone area within the selected range. The tensile strength increases with an increase in both beam power and welding speed up to a particular optimum value, and beyond that, it starts reducing. The highest hardness value is observed in the fusion zone at ‘1’ mm defocused position below the workpiece surface due to a decrease in grain size and interdendritic spacing. Ductile mode of fracture failure is found in both base material and weldment. The optimum welding condition obtained in this study yields full penetration, narrower weld width, lesser fusion zone area, minimal weld defects, and acceptable tensile strength of weldments.