His younger brother William Cochrane became first Earl of Dundonald.
He was in command of a regiment at Edinburgh in 1640, and in the following year was implicated in the plot for seizing the chiefs of the parliamentary party.
He was arrested, but after being released on bail, he joined Charles I at York in 1642.
He was sent by Charles to Denmark to solicit help in men or money; he returned with the Danish ambassador, who was instructed to attempt to mediate between the king and the parliament, and was then arrested in London.
He was subsequently employed in raising money for the royal cause in Hamburg, Danzig, and Poland.