Metal and metal oxide NPs have shown to be perfectly synthesized by using plant extracts with high efficiency, low cost and low toxicity. Our goal was to synthesize ZnO NPs by using an extract of pomegranate seeds and investigate the anticorrosion, antimicrobial and antioxidant properties of the synthesized ZnO NPs. The results have shown that the use of pomegranate in the green synthesis of ZnO NPs gave a good yield, with a low cost and non-toxic approach. The electrophoretic deposition (EPD) was used to coat stainless steel (S.S) by synthesized ZnO NPs in an alcoholic solution at room temperature producing a good coating against corrosion. The corrosion properties were investigated in a saline solution and a temperature range of (293–323) K. The effect of ZnO NPs against the growth of two Gram-negative bacteria Escherichia coli and Klebsiella sp., as well as the two Gram-positive bacterial strains Staphylococcus epidermidis and Staphylococcus aureus, as well as Candida albicans was at a very good scale. ZnO NPs have shown good properties as antioxidants to scavenge DPPH radicals. These therapeutic properties of ZnO NPs make them valuable in the medical field.