A younger son of a noble family of Brabant, he served under Duke Alessandro Farnese and against the Turks before entering the service of Duke Maximilian I of Bavaria, founder of the Catholic League. After the outbreak of the Thirty Years War, he commanded the army of the Catholic League, which with the imperial army put down the Bohemian Protestant forces at the White Mt. (1620).
In the next phase of the war, centering about the Palatinate, Tilly was chief commander against Ernst von Mansfeld, Christian of Brunswick, and others. He lost to Mansfeld (April 1622), but won at Wimpfen (May) and Höchst (June) and also at Stadtlohn (1623). After King Christian IV of Denmark entered the war (1625) Tilly and Albrecht von Wallenstein were the chief generals to oppose him. In 1626, aided by some of Wallenstein's troops, Tilly was victorious at Battle of Lutter (1626). When Wallenstein was removed from command of the imperial army in 1630, Tilly was given command of that army also, but against king Gustavus Adolphus of Sweden he was unsuccessful.
On May 20, 1631, Tilly and Count Pappenheim stormed Magdeburg. Tilly's troops massacred the populace and sacked the city, although he tried to check the violence. Later in 1631, Tilly was thoroughly defeated by Gustavus Adolphus at the Battle of Breitenfield. The next year he was again defeated by Gustavus Adolphus at the crossing of the Lech, where Tilly was mortally wounded.