Some sources credit Colonel Edward Donald Malcolm and his kin of Poltalloch in the Argyll region of western Scotland as an originator of this breed in the 19th century. It is thought that the breed gained its white coat after Colonel Edward Donald Malcolm's red terrier was mistaken for a fox and shot. Thus, the breed was only to be white in colour as to help distinguish it from its quarry. Other sources credit the 8th Duke of Argyll (Chieftain of Clan Campbell) as an originator.

The Westie came to the United States in the early 1900s, originally proclaimed Roseneath Terrior. The name was changed to manifest the breed's origins.

Some dog breeders and lovers incorrectly believe that Westies developed from white dogs in the litters of Cairn Terriers.