The two met on the set of HBO comedy "Entourage" last year, and according to a source close to the couple, their work schedules played a role in ending their romance.
"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," the source said.
On screen, the romance between the two fizzled out for similar reasons.
"It's ironic, because in the recent season finale of 'Entourage,' Jamie tells Turtle that she has to go to New Zealand to shoot a movie, and it causes problems, so it's ironic but that's what their lives are like," the source, who is close to the couple, told the mag.
Jamie-Lynn, 28, is best known for her work as Meadow Soprano, daughter of mob boss Tony on "The Sopranos." She also recently wrapped up playing Natalie, a love interest of Daniel Meade on "Ugly Betty."
Related Content from AccessHollywood.com:
VIEW THE PHOTOS: The Crazy Shenanigans Of The Cast Of 'Entourage'
PLAY IT NOW: Jeremy Piven: If 'Entourage' Wasn't Getting Better 'We Should Stop'
PLAY IT NOW: 'Entourage' Season 6 Premiere - Ladies Night!