VINCE VAUGHN has a bit of advice for his new pal ROBERT PATTINSON: Dump your cheating girlfriend Little Miss Trampire!

The two actors struck up a friendship recently while discussing a new film project, and a source says 26-year-old Robert opened up to the older and wiser Vince, 43, about his troubled relationship with actress Kristen Stewart.

The young thesps split last year year after Kristen admitted she’d had a fling with Rupert Sanders, who directed her in “Snow White & the Huntsman.” But Hollywood heartthrob Robert soon took her back.

“Vince said, ‘That’s a mistake – a big one,’” the source revealed. “He told Rob he knows how easy it is to fall into a routine, but when your girl cheats on you, you should take that as a sign that you should probably end things.”

Robert fell for Kristen, 23, during the course of filming their five blockbuster “Twilight” films. Vince certainly is familiar with on-set romances – he began dating Jennifer Aniston while they were working on the romantic comedy “The Break-Up.” They parted ways in 2006, and in 2010 Vince married Canadian-born realtor Kyla Weber, with whom he has a 2-year-old daughter.

“Vince said he and Jennifer had a great time together, but he can’t imagine settling down with someone at 26, like Rob is doing – especially someone who cheated on him,” said the source.

“Vince told Rob he was 40 before he was done sowing his wild oats.”

On April 5, Vince and Robert hit the town with mutual friend Joaquin Phoenix, attending a private party at L.A. restaurant Larchmont before heading off for drinks at the hip bar Por Vous. But despite the blossoming friendship, another insider says the handsome Brit isn’t ready to follow Vince’s sage advice.

“Vince got him thinking, for sure,” the insider added, “but there’s a level of comfort he has with Kristen that he’s scared of losing.”