Károlyi was appointed ambassador at Berlin in 1866 at the time of the rupture between Prussia and Austria, and after the Seven Weeks War was responsible for the negotiation of the preliminaries of peace at Nikolsburg. He was again sent to Berlin in 1871, acted as second plenipotentiary at the Berlin congress of 1878, and was sent in the same year to London, where he represented Austria for ten years. He died in Tótmegyer, which is now in Slovakia.