Like other types of working dog, Welsh Sheepdogs are normally bred for their herding abilities rather than appearance, and so they are generally somewhat variable in build, colour and size.

Welsh Sheepdogs are of collie type, usually black-and-white, red-and-white or tricolour, and merle markings may occur over any of these combinations.

Over many decades the Welsh Sheepdog has largely been replaced for working sheep in Wales by the Border Collie, a standardised breed.

At one time there existed many sheep-herding dogs peculiar to Wales; during the 18th century Welsh drovers taking sheep for sale took with them five or six sheepdogs as "herders on the narrow roads, guards against highwaymen, and providers of game on the route".

[1] Welsh Sheepdogs are primarily herding dogs who have a natural ability with large flocks of sheep or cattle.