This study focused on the use and application of microbial Nano- biotechnology, specifically its impact on tomato plant traits and soil microbial quality. In this regard, the microalga Scenedesmus obliquus was utilized for the green biosynthesis of zinc nanoparticles to be applied along with microalgal cell extract as a foliar fertilizer to enhance the growth and productivity of tomatoes. Biosynthesized ZnO-NPs at concentrations of 150, 200, and 250 ppm were used as foliar spray in batches with or without microalgal extract (3 cm/L) on tomato plants. For comparison, chemically synthesized ZnO-NPs at the same concentrations were used. Results showed that all interaction treatments showed statistically similar or higher values for each trait compared to the corresponding control groups (control without algae and without NPs). The treatment with algal extract combined with 250 ppm of bio-NPs demonstrated the most significant increases: 37.0% increase in total fruit yield, 43.1% increase in marketable yield, 369.4% increase in total microbial activity, 298.8% increase in dehydrogenase activity in soil, and increases of 74.8%, 182.7%, and 104.2% in zinc accumulation in root, leaves, and fruit, respectively, compared to the control treatments. These results suggest that phyco-synthesized ZnO NPs may stimulate activity in meristematic cells, potentially by activating essential biochemical pathways, leading to enhanced biomass accumulation in tomato plants.