"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.