Fairfax graduated from Magdalen College, Oxford in 1675 and served in the Yorkshire Militia under the Earl of Danby.

In 1694, William III made him Colonel of a Regiment of Foot and he was promoted to Brigadier in 1696, shortly before the Treaty of Ryswick ended the war in 1697.

In 1690 and 1695, he was a Member of Parliament generally supporting the Tory interest, although the modern concept of political parties did not yet apply.

[2] He was able to sit in the English Parliament because his title was part of the Scottish peerage; after the 1707 Act of Union, Scottish peers were disqualified and he was required to give up his seat.

[3] In 1704, Fairfax obtained a three-year licence from Queen Anne to search for wrecks and treasure in the West Indies but the venture was a financial failure.