Abstract: A sidecar for a bicycle comprised of an accessory rear mounting frame, four elongated mounting members an attachment for sidecar wheel and a framework for supporting a load. The accessory rear mounting frame extends from the rear axle of the bicycle to the seat post or the seat tube of the bicycle. Two elongated mounting members extend from the load supporting frame to the accessory rear mounting frame. Two more elongated mounting members extend from the load supporting frame to the forward structural tubing of the bicycle frame. And an attachment member, on the opposite side of the load supporting frame, and located forward of a line formed by extending the rear axle of the bicycle, comprises a support for an axle for the sidecar wheel. In one preferred embodiment each elongated mounting member and the accessory rear mounting frame has adjustments which allow the sidecar to be attached to various sizes of bicycle frames.