A glass run channel assembly which is made of an elastic polymeric material and which is capable of being mounted to a vehicle, including: a first long glass run channel, a second long glass run channel and a connecting glass run channel which connects the first and second glass run channels, the connecting glass run channel comprising a base bottom portion. The base bottom portion is provided with a projection portion which projects from an outer circumferential side surface of the base bottom portion. The projection portion includes at least a portion of a reinforcing member. The reinforcing member is molded in advance from a material which is harder and more rigid than the elastic polymeric material of the connecting glass run channel, and the reinforcing member includes a base portion arranged at the base bottom portion and a trunk portion which projects towards an outer circumferential side.