Siegfried Lenz was born in Lyck, East Prussia (now Ełk, Poland), the son of a customs officer.

According to documents released in June 2007, he joined the Nazi Party at the age of 18 on 20 April 1944 along with several other German authors and personalities such as Dieter Hildebrandt and Martin Walser.

Shortly after the German surrender at Lüneburg Heath he deserted and was held briefly as a prisoner of war in Schleswig-Holstein.

In 1951, Lenz used the money he had earned from his first novel, Habichte in der Luft ("Hawks in the air"), to finance a trip to Kenya.

Together with Günter Grass he became engaged with the Social Democratic Party and championed the Ostpolitik of Willy Brandt.

As a supporter of rapprochement with Eastern Europe, he was a member of the German delegation at the signing of the Treaty of Warsaw (1970).

In October 2011, he was made an honorary citizen of his home town Ełk, which had become Polish as a result of the border changes promulgated at the 1945 Potsdam Conference.