The prosecution's most important and final witness, Cohen acknowledged on his last day of testimony that he pocketed most of a sum of money that was meant for a technology company that did work for Trump's company.
"I just felt it was almost like self-help," Cohen said.
Donald Trump watched as his former 'fixer' Michael Cohen admitted stealing from him. (AP PHOTO)
Cohen's admission that he had stolen from his then-boss, first raised by defence lawyers on cross-examination, could hurt his credibility with jurors who will be charged with deciding whether Trump should be found guilty at the first trial of a former US president.
Shortly after Cohen left the witness stand, prosecutors rested their case and Trump's lawyers began calling witnesses of their own.
One of them drew a reprimand from the judge after he expressed dissatisfaction, prompting the judge to momentarily clear the courtroom.
"If you don't like my ruling, you don't give me side eye and you don't roll your eyes," Justice Juan Merchan told Robert Costello, a lawyer called by the defence team to testify.
Trump's lawyers have said they do not plan to call many witnesses, and it was unclear whether Trump himself will testify.
Cohen, 57, said he paid roughly $US20,000 in cash in a paper bag to a tech company out of the $US50,000 that it was owed and kept the rest. The Trump Organisation later reimbursed him $US100,000 in total.
He said he stole the money because he was upset about his annual bonus being cut after he fronted $US130,000 of his own money to buy the silence of porn star Stormy Daniels, who was threatening shortly before the 2016 election to go public with her account of an alleged sexual encounter with Trump.
New York prosecutors say Trump broke the law by covering up that payment to Daniels.
Cohen testified that he discussed that payment more than 20 times with Trump in October 2016, at a time when Trump was facing multiple accusations of sexual misbehaviour.
Cohen previously testified that Trump worried that Daniels' story would hurt his appeal to women voters. That undercut the argument by Trump's legal team that he was seeking only to protect his family from embarrassment.
But as a convicted felon and admitted liar, Cohen is a problematic witness.
Testifying for the defence, Costello said Cohen told him after a 2018 FBI raid that he did not have any dirt on Trump to offer prosecutors.
"He said, 'I swear to God, Bob, I don't have anything on Donald Trump,'" Costello said, referring to Cohen.
Costello also said Cohen told him numerous times that Trump knew nothing about the payment to Daniels.
Cohen has previously testified that he lied to Costello because he was worried he would relay to Trump any indications that he might co-operate with prosecutors.
The first former president to face a criminal trial has pleaded not guilty to 34 counts of falsifying business records to cover up the payment to Daniels, who had threatened to go public with her account of an alleged 2006 sexual encounter - a liaison Trump denies.
If he chooses to testify, Trump, 77, will have the opportunity to convince jurors that he was not responsible for the paperwork at the heart of the case, and rebut Daniels' detailed account of their meeting in Lake Tahoe, Nevada.
He would not be restrained by a gag order that bars him in other settings from criticising witnesses, jurors and relatives of the judge and prosecutors.
