The actor opened up to ET's Carly Steel on Sunday at a press junket for his upcoming film, The Glass Castle, dishing on the hotly anticipated standalone film, and the performance of Alden Ehrenreich, who stars as a young Han Solo.
"He's a great actor and a great guy, [with a] great sense of humor," Harrelson, 56, shared. "I think a lot of humor comes through what he's doing. I think it could be one of the funnier Star Wars movies."
While the still-untitled Young Han Solo project won't be released for some time, Harrelson's upcoming drama, The Glass Castle is due out next month. In the film, based on a real-life memoir, Harrelson stars as an imaginative but alcoholic father to a young woman named Jeannette Walls, played by Brie Larson.
Larson joined Harrelson at the junket, and opened up about their on-screen relationship and how they brought realism to the challenging family dynamic.
"I think what makes a powerful story is the universal aspect of it, the side of it that you feel like kind of goes beyond the specifics," Larson said. "My upbringing wasn't anything like Jeannette's, but the sense of complication and misunderstanding and love that comes with growing up in a relationship with your family is, I think, very normal."
Larson and Harrelson have actually had a close connection outside of working together on their current project. In fact, it was Harrelson who introduced his young co-star to fellow Oscar winners Jennifer Lawrence and Emma Stone -- who had both worked with him in the past.
The girls formed a close connection and soon became good friends, and Harrelson told ET it was obvious to him that they'd all get along.
"There's a lot of similarities. They're all super talented, very smart, very funny, and kind of dazzling people, each of them!" he explained. "It was pretty clear they'd all get along."