In a wide-ranging speech in which he touted his own "landslide" victory in the Republican primaries, Trump cast Pence as a perfect complement for the White House: a veteran of government, a man with a Midwestern sensibility and strong Republican credentials as a job creator and budget balancer.
"Indiana Governor Mike Pence was my first choice, I've admired the work he's done, especially in the state of Indiana," Trump said at an event in New York City.
"And one of the reasons is party unity, so many people have said, party unity. Because I'm an outsider," he added in explaining his decision.
Trump and Pence made their debut just two days before the beginning of the Republican National Convention in Cleveland, where delegates from around the country will convene to officially nominate the pair as their party's ticket for the Nov. 8 election.
Frequently straying from the notes on the lectern, Trump talked about himself and likely Democratic rival Hillary Clinton, often detouring from the purpose of the event: to introduce a little-known politician to the broader public.
"Back to Mike Pence," Trump said, interrupting himself during a lengthy explanation about why evangelical voters support his candidacy. He then read a series of statistics highlighting the job growth in Indiana.
"He looks very good," added the New York real estate mogul, who is known to comment openly on people's appearances.
Trump had a bit of a winding path to settle on Pence, a devout Christian and conservative. He postponed his planned Friday announcement after the deadly attack in Nice, and saying he had not made his "final, final decision," Trump privately had second thoughts on who to pick in late-night conversations on Thursday, said a Republican source familiar with the situation.
Trump had been annoyed that the element of surprise had been taken away by the leaking of Pence's name, the source added. Trump ended up announcing Pence as his running mate on Twitter on Friday.
Saturday's event in a New York City hotel ballroom had few of the traditional hallmarks of what is arguably one of the most important decisions for a presidential candidate. Before it started, supporters listened to the Rolling Stones song "You Can't Always Get What You Want," a tune in regular rotation at Trump events.
There were no "Trump Pence" signs distributed to the crowd or adorning the room. The two appeared together on stage only briefly - each standing out of view while the other one spoke.
On stage, they made scant eye contact and shook hands rather than raising arms together in the classic pose of running mates. Neither offered anecdotal stories about their private time together.
Pence, in sharp contrast to Trump, delivered a prepared speech, discussing the love of his wife and country and his adoration for Ronald Reagan. He gave a full-throated call to fellow Republicans to back Trump.
"Lets come together as a party, as a people, as a movement, to make America great again and that day begins when Donald Trump becomes the 45th president of the United States of America," Pence said.
Trump has struggled to bridge the gap between himself and the establishment and conservative wings of the party. The drastically different styles highlighted Pence's ability to provide a complementing tone to the presidential ticket.
It's unclear when the two will appear together again. Pence heads back to Indiana for a solo event on Saturday night, and the Trump campaign hasn't released a schedule for the convention that would include a joint appearance.
The pair recorded an interview with CBS's "60 Minutes" that is scheduled to air on Sunday night.
One of their big challenges will be to brook the policy differences in public. Pence gave a nod to that by saying "strong Republican leadership can bring about real change."
Trump has made renegotiating trade deals a central theme of his campaign, while Pence has spoken in favor of trade agreements. In an appearance on Friday night on Fox News, Pence offered a moderated take on trade, saying he agrees with Trump that deals should be renegotiated.
He also softened his vocal opposition to Trump's call to temporarily ban Muslims from entering the United States.
"I am very supportive of Donald Trump's call to temporarily suspend immigration from countries where terrorist influence and impact represents a threat to the United States," Pence told conservative Fox News commentator Sean Hannity.
Pence added that he supports Trump's call for building a wall along the U.S. border with Mexico.