Hospital-acquired infections involving carbapenem-resistant Acinetobacter baumannii (A. baumannii) and extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae pose significant challenges in the intensive care units. The lack of novel antimicrobial drugs amplifies the urgency to explore innovative management strategies. Nanotechnology, with its ability to generate nanoparticles possessing specific properties beneficial in drug delivery and nanomedicine, stands as a pivotal research domain. The objective of this study was to synthesize, for the first time, biologically silver nanoparticles (Ag-NPs) from Lavandula mairei Humbert (L. mairei) plant. The biosynthesized Ag-NPs were characterized by UV-visible spectral analysis, X-Ray diffraction Analysis, Fourier transform infrared spectroscopy analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy. Subsequently, the antibacterial and antioxidant activities of Ag-NPs were assessed using the micro-dilution method, DPPH test and FRAP assay, respectively. The green-synthesized Ag-NPs exhibited high antibacterial activity against ESBL-producing multidrug-resistant (MDR) strains and against carbapenem-resistant and non-carbapenem-resistant strains of A. baumannii, as well as a very interesting antioxidant activity. The present study suggests that these results hold very promising for the potential application of biologically synthesized Ag-NPs from L. mairei (Ag-LM-NPs) in the invention of novel antibacterial and antioxidant agents.