In 1963, Kaufmann married Tony Curtis, whom she had met during the filming of Taras Bulba (1962). They had two daughters, Alexandra (born 19 July 1964) and Allegra (born 11 July 1966). They divorced in 1968. Kaufmann resumed her career, which she had interrupted during her marriage.
On German TV, Kaufmann has admitted to have had an affair with Warren Beatty.
Kaufmann is also a successful businesswoman, promoting her own cosmetics products line that sells well in Germany. She has written several books about beauty and health, as well as two autobiographies. She speaks three languages: German, English, and French.