The measure was taken in the framework of the investigation of Trump’s purported connections to Russia and alleged interference in the 2016 election.
The agents appeared at Manafort's home without warning before dawn on July 26 and used a search warrant to seize documents and other materials, the Washington Post reported, citing people familiar with the investigation.
The raid took place just one day after Manafort met voluntarily with staff for the US Senate Intelligence Committee and began handing over documents related to the Russia probe.
The significance of the records seized by FBI agents working with special counsel Robert Mueller was unclear, the report said.
Russia has repeatedly denied interfering in the vote, insisting that it does not meddle in the internal affairs of other countries.
Trump has also strongly rejected accusations that his campaign colluded with Moscow in the run-up to the election and has called Mueller's investigation a "witch hunt."