Most work on fiber grating sensors has focused on fiber gratings written onto ordinary single mode optical fiber. The resulting sensors can sense one parameter either axial strain or temperature severely restricting their application with respect to structural health monitoring of composite materials. Each fiber grating written into birefringent optical fiber results in two effective grating sensors. By writing one grating two parameters may be sensed and by writing two four parameters can be measured. These multi-axis fiber grating sensors can be used to sense transverse strain, transverse strain gradients as well as axial strain and temperature. When these sensors are embedded into adhesive joints or composite structure they are able to locate and detect damage including delaminations, cut tow, and cracks. This paper provides an overview of multi-axis fiber grating strain sensors and outlines a series of examples of their application to health monitoring of aerospace platforms.