"I have accepted the invitation of President Enrique Pena Nieto, of Mexico, and look very much forward to meeting him tomorrow," Trump tweeted Tuesday night.
The Republican nominee will be joined on the trip by former New York City Mayor Rudy Giuliani and Sen. Jeff Sessions, the campaign said Tuesday.
The office of the Mexican president confirmed the meeting, tweeting that Trump accepted the invitation and that Pena Nieto looked forward to the meeting.
Trump didn't mention the upcoming trip at an appearance in Washington state Tuesday night, sticking mostly to his stump speech, but he did plug his much-anticipated address scheduled for Phoenix on Wednesday.
"Big speech on immigration, we’ll be talking about that. Arizona tomorrow night."
Earlier in the day, two senior-level campaign sources confirmed to ABC News that the Republican presidential nominee was considering a trip to Mexico.
Hillary Clinton's campaign responded swiftly to news of the trip. Communications director Jennifer Palmieri said in a statement, "What ultimately matters is what Donald Trump says to voters in Arizona, not Mexico, and whether he remains committed to the splitting up of families and deportation of millions."
On Aug. 16, Pena Nieto said of Trump, "I have never met him. I can't agree with some of the things he has said, but I will be absolutely respectful and will seek to work with whoever becomes the next president of the United States."
Last week during a town hall with Fox News' Sean Hannity, Trump was asked about Pena Nieto's comment.
"I'd meet with him," Trump said. "Absolutely, I'd meet with him."
Pena Nieto said in March that Mexico would not pay for a border wall under any circumstances.
The news of the visit came the day before Trump is expected to lay out his immigration plans in a speech Wednesday evening in Phoenix, joined by his running mate, Gov. Mike Pence.
ABC News' Liz Kreutz contributed to this report.