Abstract: A guard assembly that is mountable to a bicycle so as to maintain a dog in position alongside the bicycle when riding it. A U-shaped, rearwardly opening enclosure is defined by a lateral support extending from the bicycle frame and a plurality of rearwardly extending bars mounted to the outer end of the lateral support. An attachment for a short leash is provided on a middle portion of the lateral support, so that the dog will remain within the enclosure while walking or running alongside the bicycle. The rearwardly extending bars are spaced apart vertically so as to extend longitudinally past different parts of the dog's body. The upper and lower bars are spaced inwardly so as to be relatively close to the dog and therefore confine it against outward movement, while the middle bar is offset outwardly to accommodate motions of the dog's shoulders and hips.