In 1988, 1989 and 1993 he won the Davis Cup as a player with the German team , and the World Team Cup in 1989 and 1994 . His biggest single success was the 1988 quarterfinals of Wimbledon .
From 1998 to 2002 he was the coach of the B-team of the German Tennis Association . From 2003 to 2012 he was the captain of the German Davis Cup team and also coached the team at the World Team Cup . He won this trophy with the team in 2005 and 2011. In 2008 he also took on the responsibility of tournament director of the BMW Open .
Due to internal disputes with the Davis Cup players around Philipp Kohlschreiber and the feeling of lack of support from the DTB, Kühnen announced on October 31, 2012 that he would not renew his contract as captain of the German Davis Cup team.