"I can confirm the split with no additional comment," Barrymore's representative told People magazine.
The couple had dated for about a year and will soon be seen together on the big-screen in "He's Just Not That Into You."
Barrymore said of her relationship in the March issue of Vogue, "My cheeks hurt, I'm so happy."
The former child star has appeared in the movies "ET: The Extra-Terrestrial," "The Wedding Singer," "Ever After" and "Music and Lyrics." Long's film credits also include "Accepted," "Dodgeball" and "Live Free or Die Hard."