A source confirmed the two actors have decided not to get married.
U.S. & World
"The decision was mutual," the source told the mag.
"Transformers" star Megan, 22, and former "90210" regular Brian, 35, became engaged in November 2006.
Last year, Megan told People, she was hoping for a "small" wedding to the "Terminator: The Sarah Connor Chronicles" actor.
Despite their called off engagement, the source told People the couple are "still friends."