Researchers have been interested in nano ZnO in recent years because of its special qualities, which include customizable size, shape, and surface charge. For commercial use, nano ZnO can be made chemically or mechanically. Nonetheless, the world is now aware of the environmental issues these practices are causing. To address the environmental issues, green production of nano ZnO has emerged as a major area of interest. Natural materials including plant extract, microorganisms, fungus, and algae are enhanced with bioactive phytochemicals and hence they can be utilized as both structural stabilizers and reductants in this green method. In comparison to chemical synthesis, green synthesis is a simple method for producing nano ZnO with superior characteristics. The vast range of applications of nano ZnO in numerous fields has increased due to the rapid growth of nanomaterial fabrication. The growing need and application of nano ZnO, however, raises questions about its molecular and cellular toxicity as well as its biocompatibility with human cells. As a result, this analysis has also included a thorough and detailed discussion of the toxicological issues of nano ZnO.