Directors Phil Lord and Christopher Miller introduced Ehrenreich at the Star Wars Celebration "Future Filmmaker Panel" Sunday in London.
"This is the best kept secret in Hollywood," Lord joked, referring to the months-long rumors of his casting.
The filmmakers said 3,000 actors auditioned for the role. Lord added that Ehrenreich, 26, "was the first person to audition."
The young actor, best known for his role in "Hail, Ceasar!" and the Woody Allen-directed film "Blue Jasmine," did multiple screen tests, including one with Chewbacca.
It seems that fans have approved of the casting, including The Force Awakens" star John Boyega, who surprised attendees at the event.
Speaking about Ehrenreich, Boyega joked, "Look at him, he's smiling just like Han Solo."
Lord, 41, and Miller, 40, also explained why Han Solo was perfect for a standalone film in the "Star Wars" franchise.
"The dichotomy of this grouchy, seemingly cynical guy who has the biggest heart in the galaxy ... to me, that’s a great character to make a movie about," Lord said.
Miller added: "He's a maverick, he's a scoundrel, he's clever, but he's not smart. And he wants to present himself as a cool tough-guy, but in the end he always does the right thing, and that's why you love him so much."
Director Rian Johnson also revealed big news about the forthcoming "Star Wars: Episode VIII," out in 2017, which apparently filmmakers have been calling "Space Bear" as a code name.
"This movie is going to start right were the last one left off," Johnson teased. "That final scene in 'VII,' I want to see what happens next."
Johnson, 42, added that the "second film is where we start zooming in on the characters and getting to the heart of them, challenging them, and pushing them deeper."