As a young man he saw military service in the Low Countries, where he commanded a company of foot under Sir Francis Vere.

In 1586 he offered his services to James to suppress a rebellion under Lord Maxwell; and on the death of Elizabeth he was, with six of his nearest kindred, one of the first Englishmen who went to Scotland to swear fealty to the new king.

He drew up a statement of his services, and on 4 May 1627 was created Lord Fairfax of Cameron in the Peerage of Scotland; the grant was facilitated by a payment of £1,500.

He was buried, by the side of his wife, who had died in 1620, in the south transept of All Saints' Church, Otley, where a large altar-tomb, surmounted with their effigies, still commemorates their virtues.

Fairfax is said in Analecta Fairfaxiana to have written a number of works: a discourse, containing 150 pages, entitled 'Dangers Diverted, or the Highway to Heidelbergh'; 'Conjectures about Horsemanship'; 'The Malitia of Yorkshire'; a tract on the Yorkshire cavalry and against horse racing; 'The Malitia of Durham'; 'Orders for the House,' &c. The last of his works, The Order for the Government of the House of Denton, lays down in great detail the duties of every servant in his household.

Two other sons are stated by Thoresby to have died a violent death in the same year: Peregrine at La Rochelle and Thomas in Turkey.