Mortlach was founded in 1823 by James Findlater, on the site of an earlier illicit still, and was the first legally licensed distillery in Dufftown. Ownership changed hands several times in its first decades; George Cowie became a partner in 1853 and sole owner by 1867, and his son Alexander Mitchell Cowie later introduced the distillery's unusual 2.81-times partial distillation and its traditional worm-tub condensers, which still shape Mortlach's character today. William Grant, who went on to found Glenfiddich, worked at and managed Mortlach for twenty years before starting his own distillery.
In 1923 Mortlach was bought by John Walker & Sons, and most of its output has gone into Johnnie Walker blends ever since. It joined the Distillers Company in 1925, passed to Guinness in 1986, and became part of Diageo when Guinness merged with Grand Metropolitan in 1997. Mortlach is nicknamed the Beast of Dufftown for its rich, meaty spirit.