Overhead door decelerator assemblies and associated devices, systems, and methods are disclosed herein. In one embodiment, a door assembly includes a door, an elongated door track, and a brush proximate the door track. The door includes a guide member extending outwardly from a side edge portion of the door. The brush is positioned such that moving the door between open and closed positions causes the guide member to deflect a resilient portion (e.g., a plurality of bristles, a plurality of flaps, or a blade) of the brush at regions of the resilient portion consecutively positioned along the length of the brush. The brush can be positioned away from the door when the door is in the closed position and in contact with a portion of the door when the door is in the open position.