Photo Credit: FOX
"He's just so good looking, and he's a really nice person," the actress, 34, gushed to Entertainment Tonight, about her costar.
"I am so lucky," Witherspoon continued. "He's so amazing and wonderful and sweet and just the nicest guy, too, so you can just add that to the soup."
Witherspoon recalled her first meeting with the Twilight star, which was actually for the 2004 movie Vanity Fair. (Pattinson was set to play Witherspoon's son, but his scene was eventually cut from the film.)
"He was walking down this corridor, and I turned to the director and I said, 'That's my son? He's so good looking,'" she says. "I was like, 'He's so hot!'"
Though Witherspoon and Pattinson, 24, play lovers in their new film, the new pals have a hard time being serious on set.
She says: "All we do is just laugh and joke around."
Water for Elephants hits theaters on April 22.