Trump wrote that Cohen did "terrible" things that were "unrelated to Trump" and said that he believes Cohen should "serve a full and complete sentence".
President Trump on Monday highlighted a contrast between a former ally and a current one, and he hopes the former ally spends a long time in prison.
In a follow-up tweet, Trump praised his longtime ally and Republican operative Robert Stone for recently stating that he would "never testify" against him.
While Washington is focused on memorializing former President George H.W. Bush, Mr. Trump on Monday morning, at least on Twitter, has been focused on whether his associates defend him or not.
A prominent conservative writer at the heart of Robert Mueller's ongoing Russian Federation probe filed a criminal complaint against the special counsel this week; accusing the federal investigator's team of seeking "false testimony".
The tweets add to mounting questions about whether Trump is taking steps to improperly influence witnesses in an investigation that has enraged him and shadowed his administration.
Cohen's defense attorneys have asked that the NY lawyer not serve any prison time after Cohen last week admitted to lying to Congress that Trump had ended his real estate pursuits in Moscow during the early stages of the 2016 contest for the Republican presidential nomination, while actually continuing to brief Trump on a possible deal that eventually fell through.
Trump himself tweets constantly about the "Witch Hunt", and Giuliani plays ball with tweets of his own.
After the plea deal, Trump described Cohen as weak and a liar and said he himself did nothing wrong in relation to the Moscow project. George Conway posted the U.S. Criminal Code citation for witness tampering.
Trump accused Cohen of fabricating stories about his Russian Federation dealings to minimize his sentence on multiple counts of tax evasion, financial fraud and campaign finance violations that he has admitted in federal court in NY. He's rejected the deal and says he didn't knowingly mislead investigators. "The truth is very bad for their mission!"
After tweeting about his meetings in Argentina and complaining about Democrats refusing to fund his border wall, the president turned to the Mueller investigation.