In 1639 Cary served under the Earl of Essex in the Bishops' War. The following year he was elected to the House of Commons for Newport, Isle of Wight. Initially he opposed the religious intolerance of William Laud and voted against Thomas Wentworth. However, he grew disillusioned with the tactics of John Pym and his followers and in 1642 agreed to join the government of Charles I. Granted the title Viscount Falkland he served as Secretary of State.