"He's a good dude," Usmagazine.com quoted Phillippe as saying on "The Howard Stern Show" Thursday. "I love her and I want her to be happy, and it seems like she is."
The 33-year-old actor said his divorce last year from Witherspoon, the mother of his two young children, was a "mutual" decision.
"Leading up to it, we had been spending so much time apart," he said. "That's a huge part of it. There are so many obstacles."
Stern then pressed Phillippe, star of the upcoming military movie "Stop-Loss," to dish on the many women with whom he has been romantically linked in the media. Phillippe denied liaisons with Britney Spears, Ashlee Simpson, Jennifer Love Hewitt and Angelina Jolie.
Ray Liotta sues skin care company over use of likeness
NBC reportedly holds celebs hostage to Jimmy Fallon's show