The couple has split almost a year after the actor proposed to the "Thor" beauty, reported People magazine.
"Due to conflicting family and work commitments on opposite coasts, and after much consideration, Peter and Jaimie have chosen to part ways amicably and remain good friends," their representatives said.
Facinelli, 42, and the 31-year-old were first linked in November, 2012, eight months after the actor split from his wife, Jennie Garth.
Alexander was previously linked to Milo Ventimiglia in 2010, while Facinelli was married to former "Beverly Hills, 90210" star Garth from 2001 to 2013.