A magnetic field indicator mounts to an MRI system to indicate the presence of the polarizing magnetic field. An indicator wheel is mounted to a frame and is rotatable between an energized orientation in which a red colored region is seen through a window and a de-energized orientation in which a green region is aligned with the window. A weight biases the indicator wheel in the de-energized orientation and a ferrous rod rotates the wheel to its energized orientation when the polarizing field is present.