In recent years, nanotechnology has become one of the most important and exciting avant-gardes, without exception, in all fields of science. Through nanotechnology, novel materials and devices can be industrialized with atomic precision. In general, there are three main methods for synthesizing NPs: Chemical, physical and biological, or green methods. However, the conventional chemical and physical methods include the use of toxic chemicals that are toxic in nature and using pricy devices, which leads to the development of new methods using nontoxic and eco-friendly materials. These eco-friendly methods use biological systems, microorganisms, and plant-based materials as reducing, capping, and stabilizing agents to synthesize NPs. In this study, iron oxide (Fe3O4) NPs have been synthesized using a green method, a Rhus Coriaria extract, and a conventional chemical method. A comparison between these two methods is conducted to validate the importance of the biological method. This study demonstrates, as we expected, by utilizing different characterization techniques, that the synthesized green Fe3O4 NPs, in general, possess better and enhanced properties than the chemical method. This difference is evident in the aggregation status, capping and stabilizing agents around the NPs, magnetic and thermal properties, and stability of NPs. These results, in turn, highlight the importance of the available phytochemical in the Rhus Coriaria extract as a suitable candidate for biosynthesizing Fe3O4 NPs.