Was a devoted adherent of Edward IV, by whose side he fought at the Battle of Barnet in 1471, where Warwick the Kingmaker and his brother Montagu were both killed. His influence and popularity in the North appear to have been greater even than that of his predecessors. In 1471 and 1473 he presided over important conferences with the Scots at Alnwick to regulate Border affairs and to restore some order in that distracted country. In 1482 he led the van of a large army, which was assembled at Alnwick and sent, into Scotland to avenge Scottish depredations, and succeeded in forcing Scotland to accept highly unfavourable terms.

The 4th Earl was murdered by a Mob in 1489 at Thirsk for helping to raise an unpopular tax.

His father was first cousin to (among others) Edward IV of England, Margaret of York, George, Duke of Clarence and Richard III of England. Percy himself was second cousin to (among others) Elizabeth of York, Edward V of England, Richard, Duke of York, Arthur Plantagenet, 1st Viscount Lisle, Margaret Pole, Countess of Salisbury, Edward, Earl of Warwick and Edward of Middleham. Both Perkin Warbeck and Lambert Simnel were his alleged second cousins. Percy was however the only one of the Percy family to appear to take the side of the House of York during the Wars of the Roses.