IN738 Ni-based superalloy has high-temperature strength and suitable creep properties due to the presence of a high volume fraction of γ' phase, which is widely used in the aerospace industry, including the manufacture of gas turbine blades. In this research, welding was performed by pulsed Nd:YAG laser on IN738 sheets with a thickness of 1 mm. By changing the parameters of pulse frequency, pulse duration, and welding speed, the change of welding properties was investigated. The results of microstructural investigations with optical and electron microscopes showed that the sensitivity to melting and solidification cracks decreases with increasing pulse frequency and pulse duration, the most important cause of which is the decrease in the welding cooling rate due to the increase in heat input. Contrary to most of the research, in this research, by increasing the welding speed, the sensitivity to melting and solidification cracks decreased, the most important reason for which is the elimination of the effect of plasma on the weld pool. It was found that pulsed Nd:YAG laser with pulse frequency, pulse duration, and welding speed of 21 Hz, 7 ms, and 9 mm/s, respectively, can obtain a weld with full penetration and no cracks, and the tensile and hardness test results also confirm this issue.