Shapiro announced his decision in an eight-minute video posted on The Daily Wire's Twitter.
"There are three reasons I'm going to vote for Donald Trump in 2020 when I didn't four years ago," Shapiro explained.
"You don't have to love his Twitter account to vote for him"
"First, I was simply wrong about Donald Trump on policy. Second, I wasn't really wrong about Donald Trump on character, but whatever damage he was going to do, he's already done, and it's not going to help if I don't vote for him this time," he argued. "And third, most importantly, the Democrats have lost their f---ing minds."
Shapiro specifically applauded the Trump administration's handling of tax reform, foreign policy and national security, and pro-life issues.
"I thought he would not be conservative in his governance," Shapiro said. "I was just wrong on that."
He also credited the president for becoming "the first president of my lifetime not to start any new wars."
Shapiro said Democrats and the mainstream media have become a party of "radicalism" and "must not be allowed the mechanisms of power".
"I have been very clear on my feelings about Donald Trump's character. I have serious reservations to say the least...," said Shapiro, but "you don't have to like Trump's character, you don't have to love his Twitter account to vote for him. You don't have to approve of the crazy or bad things that he says or the way he often acts."
"But," Shapiro concluded, "if you care about the Constitution, and economic freedom, and the security of the United States, you really don't have a whole hell of a lot of choice. You should vote for Trump."