The efficient treatment of many infectious diseases is hindered by uncontrolled bacterial infections and inflammation induced by reactive oxygen species (ROS). Thus, there is an urgent need for the development of multifunctional therapeutic agents that possessing both antibacterial and antioxidant features. In this study, a novel antibacterial and antioxidant agent, Ga2Se3 nanosheets (NSs), were firstly prepared by the liquid-phase exfoliation method. The Ga2Se3 NSs exhibited broad-spectrum sterilization capabilities, even including multidrug-resistant strains. Noteworthily, Ga2Se3 NSs showed a remarkable 800-fold enhancement in antibacterial efficacy compared to the bulk materials, while also demonstrating low drug resistance compared to the traditional antibiotics. Their superior antibacterial performance is primarily attributed to the disruption of basic bacterial metabolism induced by gallium and selenium components, as well as the dimensional engineering of Ga2Se3 NSs. Cellular studies further confirmed the protective effects of pluronic F127 modified Ga2Se3 NSs against oxidative stress damage, preserving cellular functions through ROS scavenging. This study highlights the superior antibacterial and antioxidant properties of Ga2Se3 NSs, which offers an alternative opportunity for addressing the drug resistance issue in treatment of certain special diseases.