The numerous potential advantages of nanotechnology have resulted in the rapid growth of nanoparticles (NPs) in biomedical fields, such as bioimaging, drug delivery, and theranostics. However, owing to the toxic effects of chemical compounds and physical procedures with high energy, many adverse effects have been associated with chemical and physical synthesis of NPs. Therefore chemical and physical approaches have certain limitations in biomedical applications. Due to the hazardous effects of the chemical and physical synthesis, green nanotechnology has emerged recently. Biological synthesis techniques based on green nanotechnology could provide reliable, safe, economical, and eco-friendly strategies for the synthesis of NPs. NPs synthesized using green nanotechnology approaches (green NPs) can show many benefits compared to the chemical and physical synthesis methods. Among various types of NPs, magnetic nanoparticles (MNPs) have garnered significant interest because of their prospective utilization in biomedical domains. In this chapter, we will try to explore green MNPs in depth. To this end, first, various types of MNPs will be introduced. Then, different green synthesis methodologies of MNPs will be discussed. Then, the biomedical utility and the potential use of green MNPs in biomedical applications are also highlighted. Finally, challenges, conclusions, and future outlooks will be provided.