Functionalized magnetic nanoparticles (MNPs) play a key role in the development of new generation sensors. In the last ten years, interest in the study and development of MNP-based sensors has grown, especially in the agro-food field. Studies report that sensors, based on different working principles (mechanical, electrical, optical, etc.), can be functionalized with MNPs, which can be applied or integrated on the materials of the sensitive part of sensors or integrated in the transducer. Furthermore, MNPs can be used by dispersing them directly in the sample; subsequently, MNPs are attracted to an external magnetic field on the active detection surface of the sensors. The importance of MNP-based sensor development is in allowing the monitoring of food quality and safety, through the rapid, selective and low-cost identification of the analytes of interest. Therefore, this chapter highlights the recent applications of these devices in the agri-food field and their applications in food quality and safety along the entire supply chain.