The emergence of multidrug-resistant bacteria has increased the need for potent antibacterial agents. Essential oils (EO) are promising alternatives; however, their volatile, unstable, and hydrophobic nature challenges their bioavailability. In this study, we describe enhanced synergistic antioxidant and antibacterial effect of stable oil-in-water (O/W) nanoemulsions (NE) formulated from blends of thyme, cinnamon bark, black pepper, and garlic essential oils, using a high-energy ultrasonication incorporating a surfactant (tween 80, HLB=15) and co-surfactant (glycerol). Average droplet size of ~44-88 nm and polydispersity index of 0.2-0.3 were determined using dynamic light scattering. The spherical shape and size of the nanoemulsions were confirmed by transmission electron microscopy. The nanoemulsions were thermodynamically stable up to three months after the heating-cooling cycle (40↔ 4°C) and freeze-thaw cycle (-21°C) respectively. GC-MS and FT-IR analysis identified structures and functional groups of diverse volatile components. DPPH antioxidant assay demonstrated >16-fold enhanced free radical scavenging capacity of NE compared to blended EO and pure oils; ABTS assay exhibited similar trend. Antibacterial effects was enhanced, with MIC values halved when the blended EO was nano-encapsulated, against a resistant extended-spectrum lactamase (ESBL) strain of K. pneumoniae from 1.25 to 0.625 mg/ml , and 0.625 to 0.312 mg/ml for E. coli, S. aureus and S. typhimurium, while it remains unchanged for P. aeruginosa (1.25 mg/ml). Scanning electron microscopy highlighted significant alteration in treated bacteria’s membrane integrity. Therefore, we have successfully formulated stable nanoemulsions exhibiting enhanced synergistic antioxidant and antibacterial activities with potential applications in the food and feed industry.