The couple started dating three months ago and were photographed as recently as last month in Mexico and all seemed to be going well.
But according to US, the split has not been that upsetting to either star.
They are not dating anymore," a source told Us Magazine.com. "And it’s not a big deal for either of them.”
Also according to US, Phillippe, 36, was seen hitting on pop star Rihanna in Los Angeles last weekend, giving more weight to the notion that at least one part of the couple has already moved on.
Seyfriend, 25, formerly dated British actor Dominic Cooper. Phillippe was married to Reese Witherspoon from 1999 to 2007 and they have two children together.