As a two-dimensional (2D) ferromagnetic (FM) materials, the MoI3 monolayer exhibits promising potential for electron spintronics applications, owing to its magnetic semiconductor traits and distinctive 2D structure. We employ DFT-based first-principles computations to examine the electronic and magnetic features of the MoI3 monolayer, utilizing defect engineering (VMo, VI, IMo, and MoI) as well as rare earth doping (RE = Sc, Y, La, Ce, Pr, Nd, Gd, and Lu). The results reveal that the defect systems exhibit half-semiconductor (HSC), semi-metallic semiconductor (HMS) and bipolar ferromagnetic semiconductor (BMS) properties and modulate total magnetic moments. In addition, doping RE atoms can significantly increase the Curie temperature of MoI3 monolayers, especially the Curie temperature of MoCeI6 monolayers reaches 315.91 K, making it a potentially viable option for achieving ferromagnetism at room temperature. These findings provide a theoretical investigation for MoI3 monolayer practical application by modulating the electronic structure and magnetic properties. © 2024 Elsevier Ltd