Malcolm was the son of Donald II. He may have supported the establishment of a Danish kingdom of York in the 940s, and he harried the north of England. He was killed in battle, possibly at Fetteresso, Kincardineshire by rebels from Moray.

Malcolm I, who died in 954, became King of Scotland in 943 and acquired Cumbria in 945 from Edmund, the Saxon king of England. On the abdication of Constantine II., Malcolm succeeded to the throne. In 945, Edmund, the Saxon king of England, ceded Cumberland and part of Westmoreland to him, on condition that he would defend that northern territory, and become the ally of England. Edred, the brother and successor of Edmund, accordingly applied for, and obtained the aid of Malcolm against Anlaf, King of Northumberland, which latter country he wasted, and carried off the inhabitants with their cattle. In the time of Malcolm I., the people of the province of Moray, in the northeast of Scotland, were a mixed race, formed of Scandinavian settlers, with Scottish and Pictish Celts. Turbulent and rebellious, they were continually at war with the sovereign, and an insurrection having occurred under Cellach, maormer of Garmorgan, Malcolm marched north to reduce them to obedience. He killed Cellach, but was, some time thereafter, assassinated in 954 at Ulurn. He was succeeded by Indulph, the son of Constantine II., and Indulph had as his successor, Duff, the son of Malcolm, who ascended the throne in 961.