The man was walking his small dog off-leash along the river near Wellington Street and McRae Boulevard when allegedly it attacked an American bulldog who was on-leash, out for a walk with its owner.
The two dogs got into a fight and the man allegedly jumped on the bulldog, punching it. When the small dog ran away, the man kicked the bulldog and threatened its owner before leaving the area.
Police are looking for the man, who is described as white, six feet tall and in his early to mid 40s with a medium build.
Anyone with information should call Guelph Police at 519-824-1212 or Crime Stoppers at 1-800-222-TIPS.