The sentence was imposed Friday in federal court in Washington.
He is the first former campaign aide to be sentenced in special counsel Robert Mueller's Russia investigation.
Papadopoulos apologized for his actions, telling a judge that he had made a "dreadful mistake" and was eager for redemption.
Prosecutors sought a sentence of up to six months, while defense lawyers asked for probation.
His case was the first to detail a member of the Trump campaign having knowledge of Russian efforts to interfere in the 2016 presidential election while it was ongoing.
This is a developing story.