The former Full House star, 31, filed for legal separation from Morty Coyle, her husband of a little more than a year, according to court documents filed in Los Angeles. The actress cited irreconcilable differences.
Sweetin is seeking custody of the pair's 2½-year-old daughter Beatrix, as well as ownership of their 2000 Toyota Avalon.
Sweetin, who was previously wed to Cody Herpin and Shaun Holguin, referred to then-fiancé Coyle as "wonderful and fantastic" in 2011.
The actress and her ex – who got engaged on Sweetin's birthday in January 2011 – kept their marriage secret for a little more than a year, telling PEOPLE they decided to make it public on their first anniversary.
Said Sweetin in 2011, "I don't think anything in the world could be better than what I have."
When reached by PEOPLE, a rep for the actress had no comment. TMZ was first to report the news of the couple's separation.
Reporting by AILI NAHAS