The production of strontium oxide nanoparticles from an aquatic plant extract is described here. UV–vis spectroscopy at ~ 220 nm was used to confirm the biosynthesis of these particles, and the color of the mixtures altered from colorless to green. The morphology of Elodea canadensis strontium oxide nanoparticles (EcSrONPs) was characterized using FE-SEM. FE-SEM images demonstrated that these particles adopted disordered, irregular shapes with agglomeration and slightly smooth surfaces. FE-TEM confirmed the results of FE-SEM analysis. These particles were also evaluated using XRD, XPS, and FTIR. The XRD pattern revealed a face-centered cubic crystalline structure at (209) and (217), while the XPS results verified the presence of both strontium and oxygen in the synthesized EcSrONPs. FTIR results confirmed that phytochemical functional groups served as capping agents during EcSrONP synthesis. In addition, zeta potential analysis confirmed the stability of EcSrONPs. Finally, the antibacterial potential of the produced EcSrONPs against Escherichia coli and Bacillus subtilis was evaluated. The largest inhibitory zone against E. coli (diameter, 22 mm) and B. subtilis (diameter, 20 mm) was observed at a EcSrONPs concentration of 24 µg·mL−1. Collectively, the findings of this research show that the biosynthesis of EcSrONPs is a viable option for developing novel materials for biomedical applications.