Kleff's life in goal of West Germany was limited due to his competitor Sepp Maier occupying the role of West Germany's leading goalkeeper in that decade, Kleff won just six caps for his country in between 1971 and 1974. His first of those six matches took place in Oslo on 22 June 1971, and was a 7–1 thrashing of Norway in a post-season friendly. Despite not making many appearances for his country, Kleff won the 1972 UEFA European Championship trophy in Brussels and the 1974 FIFA World Cup.