Bergengruen was born in Riga in 1892. After growing up in Lübeck and attending the Katharineum, he started studying theology in Marburg in 1911. He later changed to studying German philology and art history, but failed to graduate; he then moved to Munich.
Bergengruen started writing novels and short stories in 1923 and decided to become a full-time writer in 1927. While his earlier works were of a more contemplative nature and pondered metaphysical and religious questions, the Nazis' rise to power led him to write more political works. His most successful novel, Der Großtyrann und das Gericht, published in 1935, is set in the Renaissance era, but the story of a merciless tyrant playing with the weaknesses of his underlings was often seen as a clear allegory on Germany's political situation. This interpretation is doubtful, though, as most of the novel was written before the Nazi takeover in 1933. In 1936 Bergengruen was received into the Catholic Church. In 1937 he was expelled from the Reichsschrifttumskammer for being unfit to contribute to German culture.
After WWII, he lived in Switzerland, Rome, and finally Baden-Baden, where he died in 1964.