He was raised a Catholic and attended the Danzig Gymnasium Conradinum.
After working as a farmhand, a miner, and a stonemason, he enrolled at the Dusseldorf Academy of Art in 1948 to study sculpture.
He was conscripted into the Reichsarbeitsdienst (National Labor Service) in 1943 when he was 16. The very next year he was drafted into the Waffen-SS.
He was wounded in April 1945 following which he was captured by American forces and sent to a U. S. prisoner-of-war camp. He was later released.
Upon his release, he worked for a while in a chalk mine and went on to study sculpture and graphics, at the Kunstakademie Düsseldorf.
Over the next few years he worked as an author, sculptor and graphic designer before moving to West Berlin in 1953. There he studied at the Berlin University of the Arts.
He was an active participant in the Group 47, an informal but influential association of German writers and critics, organized by Hans Werner Richter. The other members included Heinrich Böll, Uwe Johnson, and Ilse Aichinger.
He was working in a publishing house when he published his debut novel, ‘The Tin Drum’, in 1959. The novel, in spite of being his first one became a hit with the readers and critics alike and established him as a rising star in the German literary world.
In 1961, he wrote a novella, ‘Cat and Mouse’, and followed it with ‘Dog Years’ in 1963. ‘The Tin Drum’, along with these books collectively comprised the Danzig Trilogy which focuses on how Nazism and World War II changed the history of Danzig.
He published the novel ‘The Flounder’ in 1977 which is based on the folktale of ‘The Fisherman and His Wife’. This work was considered to be anti-feminist and deals with the struggle between the sexes. Heavily panned by feminists, the book was harshly critiqued.
In 1999, he released ‘My Century’, which was an overview of the 20th-century's many brutal historic events. Three years later, he wrote a novella, ‘Crabwalk’ which deals with the events of a refugee ship sunk by a submarine. It became a big success.
In addition to being an author he was also involved in social and political activism and was for several decades a supporter of the Social Democratic Party of Germany and its policies.
He married Anna Margareta Schwarz, a Swiss dancer, in 1954. This union produced four children. Anna and Gunter Grass separated in 1972 after almost two decades of marriage and divorced in 1978.
He married Ute Grunert, an organist, in 1979 and remained married to her for the rest of his life.
He also had two children from other relationships, two stepsons from his second marriage, and 18 grandchildren.