Tourist Jeffrey Fowle was detained on 7th May for leaving a bilingual English-Korean Bible in a restaurant in the city of Chongjin.
Inside the book, the 56-year-old left his contact information and pictures.
It was found by a cleaner, who reported it to the police.
He was still awaiting trial, but State Department spokeswoman Marie Harf confirmed that the US government had successfully negotiated his release.
Two other men, Christian missionary Kenneth Bae and Matthew Miller, remain in custody, although Ms Harf said officials were working to secure their freedom.
Mr Fowle is on his way back to America.