The influence of Gd content on the solidification behaviors and as-cast microstructures of Ni–Mo-Cr-Gd alloy have been investigated systematically. It was found that the γ/Ni₅Gd eutectic phases were formed in the interdendritic region, which exhibits the divorced character. With the Gd adding, the γ/M₆C eutectic phases were replaced by the γ/M₂C eutectic ones. Most M₂C carbides locate at the interfaces of γ/Ni₅Gd eutectic phases or are enclosed by Ni₅Gd phases. The segregation of alloying elements was mitigated by Gd adding. Based on the thermal analysis, composition analysis and thermodynamic calculation, the solidification behaviors, and the affecting mechanism of Gd adding were briefly discussed. During the solidification process, the γ/Ni₅Gd eutectic reaction occurs first, which interrupts the solute redistribution process and thus mitigates the segregation of some alloying elements. The Ni₅Gd phases accommodate a mass of Si and keep the Si content in the residual liquid phase low, which decreases the nucleation rate of M₆C carbides. Then, the γ/M₂C eutectic phases become the dominant ones at the final stage of the solidification process. Our results are useful in future optimization and processing research of Ni-Mo-Cr-Gd alloy for applications in molten salt reactors.