A cantilever bracket mounted on two headrest supporting rods of a seat and includes two cantilevers and a post. The cantilever has one end provided with a fixing seat having a through channel through which the corresponding rod can pass, and the other end provided with a pivot seat. The post having one end provided with a supporting portion for supporting or hanging an object, and the other end provided with a first pivot which passes through pivot holes of the two pivot seats and pivotally connects the two cantilevers as a single unit of which the distance between the two fixing seats is adjustable. The cantilever bracket is applicable to seats of various headrest supporting rods with different spacings therebetween and eliminate the need for brackets of different specifications in accordance with the various headrest supporting rod spacings.