Her autobiographical account of the Holocaust, All but My Life (1957), was adapted for the 1995 short film, One Survivor Remembers, which received an Academy Award and an Emmy Award, and was selected for the National Film Registry. She married Kurt Klein (1920–2002) in 1946. The Kleins became advocates of Holocaust education and human rights, dedicating most of their lives to promoting tolerance and community service. A naturalized U.S. citizen, Gerda Weissmann Klein also founded Citizenship Counts, a nonprofit organization that champions the value and responsibilities of American citizenship. She has served on the governing board of the United States Holocaust Memorial Museum, which features her testimony in a permanent exhibit. On February 15, 2011, Klein was presented with the Presidential Medal of Freedom, the highest civilian award in the United States. In 2013, she published a children's adventure story called The Windsor Caper, which had remained hidden away since the 1980s, when it was a weekly serial in The Buffalo News.

In May 1945, Gerda was liberated by forces of the United States Army in Volary, Czechoslovakia; these forces included Lieutenant Kurt Klein,^[3] who was born in Germany and immigrated to the United States to escape Nazism. Both of his parents had been killed by the Nazis at Auschwitz. When Gerda and Kurt first met, Weissmann was white-haired, weighed 68 pounds, and was one day shy of her 21st birthday. She was wearing rags, and had not bathed in three years. Kurt simply opened a door for her, and she immediately felt human again. The two became engaged in September 1945 and got married in 1946.