Federal prosecutors snagged a huge victory when they secured two guilty pleas from Cohen.
Cohen, who is a key figure in multiple criminal investigations into him and the president, pleaded guilty to tax evasion, bank fraud, and campaign-finance violations in August as part of a Manhattan US attorney's office investigation.
Cohen said following his guilty plea that he broke election law at Trump's direction.
Last month, he also pleaded guilty to one count of lying to Congress as part of Mueller's investigation. He has been cooperating with both probes since August, and he is believed to be one of the star cooperators against Trump.
Cohen's lawyers said in a sentencing memo earlier this month that Cohen was in "close and regular contact" with the White House while drafting his false testimony.
Trump, for his part, appears to be aware of the danger Cohen poses: he has unleashed a torrent of Twitter rants against his former lawyer, at one point calling him a "rat" and accusing him of being weak.
Cohen has said that he previously felt it was his "duty" to cover up for Trump's "dirty deeds," but that he is now eager to cooperate with the government out of duty to country. He was sentenced to three years in prison last week.