U.S. District Judge William H. Pauley III said on Wednesday that Cohen deserved a harsh punishment for crimes including tax evasion, lying to Congress and arranging illicit payments to silence women who posed a risk to Trump's presidential campaign.
"I stood up before the world yesterday, and I accepted the responsibility of my actions," Cohen told Stephanopoulos.
The judge rejected arguments by Cohen's lawyers that he should be spared jail time because he cooperated in multiple federal investigations involving Trump.
RELATED: Who is Donald Trump's personal lawyer and fixer Michael Cohen?
When Stephanopoulos asked whether the president knew it was wrong to make the payments, Cohen replied, "Of course," but he did not elaborate.
"I will not be the villain of his story," Cohen said.
He added that his "blind loyalty" to Trump made him feel a duty to "cover up" the president's "dirty deeds."
"I gave loyalty to someone who, truthfully, does not deserve loyalty," Cohen said.
Cohen's crimes included evading $1.4 million in taxes and misleading Congress about his talks with Russians about a Trump skyscraper project in Moscow.
EXCLUSIVE: "I will not be the villain of his story," Michael Cohen tells @ABC News' @GStephanopoulos, saying that Pres. Trump knew it was wrong to make hush-money payments during 2016 presidential campaign.— ABC News (@ABC) December 14, 2018
Watch the exclusive interview only on @GMA. https://t.co/84huhn7jOE pic.twitter.com/PS0WZJNfpF
Trump had called for a tough sentence for Cohen, whom he labeled a liar. Cohen told ABC he no longer feels any loyalty to the president.
"My first loyalty belongs to my wife, my daughter, my son and this country," he said.
RELATED FROM ABC NEWS: READ THE FULL TRANSCRIPT OF THE INTERVIEW
The Associated Press and ABC News contributed to this report.