1977 was the greatest year in Simonsen's career. In the 1976–77 European Cup, Simonsen helped Mönchengladbach to the 1977 European Cup Final against English team Liverpool. In the final, Simonsen scored a memorable goal from a powerful shot to level the game at 1–1, but Mönchengladbach eventually lost 3–1. He was subsequently named the 1977 European Footballer of the Year, becoming the first Danish player to win that award. The race was tight, Simonsen edged past English forward Kevin Keegan by three points and French midfielder Michel Platini by four points to win the prestigious prize. The win was notable in that Simonsen's native Denmark was not among the top footballing nations in the 1970s, leaving little room for him to impress at the international tournaments.