Johnson and LaBeouf co-star in the movie The Peanut Butter Falcon, which also features actor Zack Gottsagen. LaBeouf was arrested for public intoxication and disorderly conduct in 2017 while in Savannah, Ga., to film the movie.
"It was a really kind of sad [situation]," Johnson said. "I felt very protective of him. That's a really terrifying and difficult journey for somebody to experience, and I felt really aware of that."
"We were there to make this movie, and Zack is really a phenomenal human being. You feel very awake to the truth of life and humanity and love and people and real connections when you're with him," she added.
Johnson said she thinks LaBeouf's arrest was "a very important moment" for the actor.
"I don't condemn people for their mistakes," she said. "I want them to get through it."
Gottsagen, 34, appeared with Johnson on Ellen and also had praise for LaBeouf. He said he became good friends with LaBeouf and wasn't nervous to work with the actor.
The Peanut Butter Falcon follows a young man with Down syndrome (Gottsagen), who escaprs from an assisted living facility and befriends a fisherman (LaBeouf) on the run. The film is a reimagining of Huckleberry Finn, and opened in theaters in August.