"I just wanted to confirm that, yes, they did break up," Carrie Gordon told The Associated Press in a phone interview, adding that the couple remain friends. Gordon didn't give further details.
Barrymore, 33, and Long, 30, co-star in the movie adaptation of the self-help best-seller "He's Just Not That Into You," slated for release next February.
The split comes as a surprise, given their public displays of affection since they began dating last year.
Long's big-screen credits include "Accepted" and "Dodgeball," and he's also the "Mac guy" in Apple's TV commercials. Barrymore's screen credits include "Fever Pitch," "50 First Dates" and "E.T.: The Extra-Terrestrial."
The lanky actor seemed smitten with the actress-producer, escorting her to red-carpet events including Madonna and Gucci's "A Night to Benefit Raising Malawi and UNICEF" party in New York City in February.
He was in the audience during Barrymore's recent appearance on Oprah Winfrey's talk show. Beaming, Long gushed: "She's the most compassionate person I've ever met."
"This relationship is great," Barrymore told Winfrey. "It's healthy, it's productive, and it's supportive. It's full of humor and a lot of fun."
