Trump's tweet, which came as Manafort entered the second day of his federal criminal trial, also said the "old charges" Manafort now faces "have nothing to do with" suspicions that members of the Trump campaign colluded with Russians trying to interfere with the 2016 election.
The tweet seemed to suggest that unnamed people in the government should have warned Trump about hiring Manafort before he did in 2016.
Trump's angry tweet about Manafort's case came on the heels of a series of tweets blasting special counsel Robert Mueller, who brought charges against Manafort and is investing possible collusion by the Trump campaign with Russia.
Trump tweeted that Attorney General Jeff Sessions "should stop this Rigged Witch Hunt right now before it continues to stain our country any further."
He followed up his tweet about Manafort with another one in which he raged: "Russian Collusion with the Trump campaign, one of the most successful in history, is a TOTAL HOAX."
The charges against Manafort are related to work the long-time Republican consultant and lobbyist did on behalf of pro-Russia politicians in Ukraine from 2005 through 2014. That work predates his tenure as head of the Trump presidential campaign in 2016.
Manafort is charged with bank fraud and tax crimes in U.S. District Court in Alexandria, Virginia. Mueller's prosecutors said Manafort hid up to $60 million of income in offshore accounts. They also accuse him of duping lenders with phony financial documents in an effort to maintain his luxurious lifestyle after Ukraine stopped being a source of income.
The charges do not accuse him of working with Russians or any other foreign entity to affect the outcome of the 2016 election.
But there is widespread belief, particularly in Trump's camp, that Mueller is using that case against Manafort, and another criminal case against him in Washington federal court, as leverage to get him to cooperate with prosecutors in the Russia probe.