The deal enables Manafort, who was convicted of tax and bank fraud charges by a federal court jury in Virginia, to avoid a second trial in the District of Columbia.
The agreement makes Manafort the latest member of Trump's inner circle to cooperate with the investigation that has loomed over his presidency.
Manafort, wearing a dark suit, white shirt and purple tie, appeared upbeat as he arrived in court where he quickly took his place at the podium to enter his plea of guilty to two conspiracy counts, including conspiracy to obstruct justice.