In the summer of 1986, Koeman controversially transferred to PSV Eindhoven to play for Hans Kraay's champions. Towards the end of the 1986–87 season, Kraay resigned and was replaced by Guus Hiddink, under the management of whom PSV overtook league leaders Ajax in the final weeks of the season to defend their league title. Koeman enjoyed further success with Hiddink and PSV in the following seasons, as the team also won the 1987–88 and 1988–89 Eredivisie titles and the club's first, and to date only, European Cup against Benfica in Stuttgart on 25 May 1988. PSV had also won the KNVB Cup in both 1988 and 1989, making their successes in the two years trebles and doubles respectively. In his three seasons at PSV, Koeman scored 51 goals in 98 league appearances, averaging more than one goal every two matches. During 1987–88 season, he recorded the highest scoring season of his club career, with 21 goals scored in the league.