Magnetic nanoparticles have been discovered to be promising materials for various biomedical applications; for example, they have been used for cancer detection, screening, and chemotherapy studies during the last few decades. Likewise, magnetic nanoparticles have significant antibacterial properties, and similarly, they can be applied for magnetic resonance imaging purposes. These sensors are meant to detect certain biomarkers, which are substances that can be linked to the beginning or progression of cancer both during and after therapy. Magnetic nanoparticles have several unique properties that are being employed widely in cancer therapy as drug delivery agents to precisely target the targeted spot using an external magnetic field in vivo. Magnetic resonance imaging can also be used in conjunction with antineoplastic drug treatment personalized to the individual. We have presented an overview of the different applications of magnetic nanoparticles as well as current breakthroughs in their development as antibacterial and cancer therapies in this review. In addition, the cancer targeting, possible toxicity, and degradability of these nanomaterials are briefly discussed.