A stabilizer for flexible guards provides for the stabilization and control of flexible flaps, brush type devices, and the like as used in motor vehicle mud flaps, car washes, and in conveyor systems. The present stabilizer includes a rigid structure which completely surrounds the guard(s), and which is loosely and flexibly suspended from an overlying structure. The rigid portion of the device is preferably constructed of polyvinyl chloride (PVC) pipe or tubing, or any other suitable elongate structural material (e.g., electrical metal tubing, pipe, and/or extruded metallic or non-metallic shapes, such as Tees, channels, angles, etc.). The rigid structure is preferably suspended from the overlying structure by chains at at least both ends of the device, with an additional chain(s) optionally installed at the center area of the device. The chains (or other suitably flexible attachments) provide longitudinal, lateral, and vertical movement or compliance in the event the stabilizer or stabilized guard strikes or is struck by another object, thus precluding damage to the stabilizer and/or transfer of the impact and resulting damage to the vehicle or attachment structure. The rigid portion of the device which surrounds the guard, may be weighted in order to adjust the periodic frequency of the suspended assembly, to avoid any resonant frequencies with the guard with which the device is installed. Width adjustment may be provided by forming the elongate lateral members of telescoping components.