A magnetic proximity sensor is attached to a ferrous object such that the sensor alerts a practitioner if a threshold of magnetic strength has been exceeded by bringing the ferrous object within a certain proximity to the magnet of an MRI scanner. The magnetic proximity sensor includes at least one magnetic field sensor for sensing a magnetic field strength. An alarm in communication with the field sensor alerts a practitioner that a threshold of magnetic strength has been exceeded. A battery powers the field sensor and the alarm. The field sensor may produce an output voltage corresponding to the sensed magnetic field strength, and a potentiometer may provide a reference voltage corresponding to a threshold magnetic field strength. A comparator compares the reference voltage to the output voltage, and triggers an alarm if the output voltage exceeds the reference voltage.