Abstract: The effect of aging precipitation on the stress corrosion cracking (SCC) mechanism of Ni(Fe,Al)-maraging steel was studied through the comparative characterization and analyses of the microstructures and fracture features of solid–solution and peak-aged steels. Aging precipitation exerts a chain of impacts on the deformative compatibility and electrochemical difference between the matrix and other phases or interfaces. The strength of the martensite matrix is enhanced by abundant and evenly dispersed Ni(Fe,Al) precipitates, thereby reducing the possibility of splitting across martensite laths. Meanwhile, the Volta potential difference (VPD) between the matrix and primary NbC particles increases from 11.3 to 18.60 mV. Given that most of the primary NbC particles tend to be distributed along high-angle grain boundaries (HAGBs), anodic dissolution along HAGBs accelerates. Therefore, mechanical and electrochemical factors triggered by aging precipitation are involved in the variation in SCC behavior and mechanism. The SCC susceptibility of the steel increases along with the increasing tendency for intergranular cracking.