Plant growth-promoting bacteria (PGPB) and nanotechnology integration is a potential way to increase the productivity of crops sustainably. The current research examines the combined influence of biogenic selenium nanoparticles (SeNPs) and PGPB on the growth and physiological performance of lettuce ( Lactuca sativa). Selenium-resistant bacterial strains were obtained from soil of agricultural fields and evaluated for their plant growth-promoting properties, such as phosphate solubilization, nitrogen fixation, and production of phytohormones. Lettuce seeds were inoculated with suspensions of bacteria, and then biogenic SeNPs were applied on the leaves. Growth parameters like root length, leaf length, fresh weight, and photosynthetic pigment content were measured. Results indicated that bacterial inoculation greatly enhanced plant growth parameters, and the co-application of PGPB and SeNPs further enriched chlorophyll content, protein deposition, and peroxidase activity. Of particular interest was the fact that some of the bacterial strains (NB10 and NB11) had a greater impact on selenium bioavailability, indicating strain-specificity. In addition, SeNPs alleviated oxidative stress and enhanced stress tolerance as indicated by enhanced enzymatic antioxidant activity. Statistical comparison (ANOVA and Duncan’s multiple range test) validated significant treatment differences (p ≤ 0.05). These results indicate the promise of PGPB-SeNP synergy as a bio-based approach to enhancing crop productivity and resilience while minimizing chemical fertilizer use. This research adds to the emerging nano-enabled agriculture discipline, providing scalable and eco-friendly solutions for sustainable crop cultivation.