Wade was born in Kilavally, Westmeath, Ireland. He joined the British Army in 1690 and served in Flanders in 1692, earning a promotion to Captain. During the War of the Spanish Succession (1702-13) he first served under Marlborough, being promoted to major and lieutenant-colonel in 1702. In 1704 he was on the staff of Lord Galway, distinguishing himself at Alcantara and Villa Nova in 1706 and at Almanza in 1707. He was promoted to Brigadier-General in 1708. He was second in command to James Stanhope in Minorca in 1708 before returning to Spain in 1710, where at the Battle of Saragossa he earned a promotion to Major-General.
He returned home to attempt politics before becoming involved in the suppression of the Jacobite rebellion of 1715. Wade was sent to inspect Scotland in 1724 by George I. He recommended the construction of barracks, bridges and proper roads to assist in the control of the region. Between 1725 and 1737 Wade directed the construction of some 250 miles of road, plus 40 bridges (including the Taybridge at Aberfeldy). The roads linked the garrisons at Ruthven, Fort George, Fort Augustus, and Fort William. He also organised a militia named Highland Watches, calling on members of the landed gentry. The first six companies were raised in 1725 (three of Campbells and one each of Frasers, Grants and Munros), with four more in 1739, reorganized as the Black Watch regiment.
In 1742 Wade was promoted to Lieutenant-General and made a privy councillor. In 1743 he was made a Field Marshal and appointed to joint command of the Anglo-Austrian force in Flanders against the French. He resigned from that command in March 1744, returning home to be made commander-in-chief. When the Jacobites rose again in 1745 the speed of their advance was beyond Wade. He failed to counter their march into England and was dismissed, the Duke of Cumberland heading the army for the decisive Battle of Culloden.