Depp and French model-actress Vanessa Paradis announced last week they had ended their romance after 14 years and two children together.
Rumors immediately began swirling that Depp, 49, has been dating Heard, 26, and even bought her a horse so she can ride with him when she visits him on the set of "The Lone Ranger."
"They are 100 percent dating," a source told UsMagazine.com Thursday. "He treats her really well."
The magazine's Web site said the relationship began last year when they were promoting "The Rum Diary," and Depp and Paradis were already estranged.
"They started sleeping together during the press tour," an insider said of Depp and Heard, who is bisexual and recently broke up with her girlfriend, artist Tasya van Ree.