"The campaign is grateful to Corey for his hard work and dedication, and we wish him the best in the future," according to a statement from Trump's spokeswoman Hope Hicks.
Lewandowski was fired during a meeting this morning with the candidate and campaign leaders at Trump Tower in New York City.
A senior Trump aide told ABC News that Lewandowski's firing "was a long time coming" and that the campaign "need[ed] to get everyone on the same page."
News of Lewandowski's departure was first reported by the New York Times.
Lewandowski, in an interview with CNN said that he didn’t know why he was fired.
"I don't know. I don't know the answer to that. But what I know is what we've been able to achieve in this election cycle has been historic,” he said.
Aides had grown frustrated with the lack of teamwork between Lewandowski and campaign chairman Paul Manafort, who was hired after Lewandowski. The campaign is expected to make other changes in the coming days, including new staff hires. Aides also said Trump has "complete confidence" in Manafort.
Sources told ABC News the final push came from Trump's three eldest children, his son-in-law Jared Kushner, Manafort, and other longtime aides. The sources all stressed the campaign shakeup was unrelated to any particular criticism Trump has experienced over the past week.
The ousted campaign manager denied that he had tense relationships with any of Trump’s children and remained unrelentingly supportive of Trump and Manafort during interviews after he was fired.
"I wanna say how honored I am to have been part of this team, and it’s been such a privilege to be apart of the team,” he said on CNN today.
He also denied reports that he had attempted to malign Kushner in any way, whose own power and influence has grown within the campaign, according to sources.
"I've had a great relationship with Jared...," Lewandowski said. "So I'm not sure where that's coming from."
However, it is important to note that all staffers, Lewandowski included, were required to sign a non-disclosure agreement upon joining Trump's campaign.
He told CNN that Trump called him to inform him of the decision and confirmed that he had been escorted out. "But it wasn’t security - it was a friend from the office,” he said.
The sources all stressed the campaign shakeup was unrelated to any particular criticism Trump has experienced over the past week.
Lewandowski had been with the campaign since its start. A New Hampshire native and a newcomer to the national political stage, he joined the campaign after managing the campaign of former Ohio Rep. Robert Ney. Lewandowski graduated from the New Hampshire Police Academy and worked briefly as a state marine patrol officer.
He worked for a time with the conservative PAC Americans for Prosperity, managing its regional effort; the North Carolina Board of Elections opened an investigation into that operation after allegations surfaced that it sent what the board called "misleading, incorrect and confusing voter registration mailers."
During his time as Trump's campaign manager, Lewandowski became a controversial figure in and outside the campaign. In March he was charged with simple battery after a video showed that he grabbed the arm of then–Breitbart reporter Michelle Fields at the Trump National Golf Club in Jupiter, Florida. The state's attorney declined to prosecute Lewandowski. The Trump campaign at the time said it fully believed in Lewandowski's innocence.
"Look, I think I'm a very intense person,” Lewandowski told CNN on Monday when asked if his temperament proved a problem. “When I see someone who I don’t think is working as hard as the person who's funding the campaign, who’s the campaign principal, meaning the candidate, yeah that bothers me."