Alexander, the 10th laird, was an ardent Royalist supporter of Charles I when most around him were Covenanters, the Scottish equivalent of the English Roundheads. He, like his father, was Sheriff of Aberdeen and with him the family's prosperity and prestige reached its peak. As the Civil War spread, Alexander was away from Drum fighting when the castle was besieged. In the face of General Monroe's heavy siege equipment, Lady Irvine decided to surrender quite rapidly and included a promise that her husband would give himself up. So Drum Castle received a hostile garrison, the first of four it was to endure during the Civil War.

Drum Castle was plundered three times during the Covenanting Rebellion throughout which the royalist Irvine's supported Charles I. Sir Alexander, a Royalist, was forced to conform to the Covenant. Alexander, 10th Laird of Drum, his brother Robert Federett and his two sons were imprisoned at the Tolbooth in Edinburgh several times. His son Robert died there in 1646.

in 1660, an offer of royal peerage was made to the eleventh Laird by Charles II, but was turned down because the king wouldn't pay to repair damage sustained to Drum Castle while the family had supported the king during the rebellion.