Abstract Monolayer MoSi 2 N 4 has been proposed as a promising channel material for new-generation nanodevices, owing to its superb ambient stability and exceptional electronic properties. Despite recent experimental and theoretical research revealing the interfacial characteristics of monolayer MoSi 2 N 4 in contact with metals, the effect of different metal electrode contacts on the electrical transport of MoSi 2 N 4 within the framework of device configuration remains unexplored. Using first-principles transport calculations, this study investigates the electrical properties of metal semiconductor devices with monolayer MoSi 2 N 4 placed between MoSi 2 N 4 -metal (Au, Ag, Pt, and Ti) electrodes. While n- and p-type Schottky contacts are formed in Au_MoSi 2 N 4 _Au and Pt_MoSi 2 N 4 _Pt, respectively, quasi- and entire ohmic contacts are achieved in Ag_MoSi 2 N 4 _Ag and Ti_MoSi 2 N 4 _Ti, respectively. I–V characteristics show that devices with asymmetric metal electrodes exhibit pronounced rectification behaviors. The rectification ratio of Ag_MoSi 2 N 4 _Au exceeds 10 6 , which is related to the extreme asymmetric band arrangement in devices driven by a bias polarity. These results provide valuable guidelines for the development of high-performance MoSi 2 N 4 -based electrical nanodevices.