In a statement, the celebrity couple said they decided to end their marriage but share "the same deep love and devotion to our children." They have three daughters together.
Garth, 39, and Facinelli, 38, said they remain "dedicated to raising our beautiful daughters together," and asked for privacy and respect.
Garth is best known for her role as Kelly Taylor in the 1990s TV series "Beverly Hills, 90210." She also competed in "Dancing With the Stars" in 2007.
Facinelli appeared in the "Twilight" movie franchise.
The Associated Press contributed to this report.