The pair met on the set of "Entourage" last year when Sigler joined the HBO comedy as a guest star - playing herself as the on-screen love interest of Ferrara's character, Turtle. They soon started dating in real life, too.
"They're busy with their careers, and she in particular has a couple of movies out in 2010, and others in the works for 2011, so it's just tough," a source told People magazine.
It's almost a case of art imitating life. In the recent season finale of "Entourage," Jamie told Turtle that she was leaving for New Zealand to film a movie, which effectively ended their romance.
Sigler, who grew up in Jericho, is best known for playing Meadow Soprano on HBO's "The Sopranos." In 2003, she married A.J. DiScala, who was her agent at the time. They divorced two years later. Most recently, she's been on ABC's "Ugly Betty."