The 23-year-old Modern Family star has alleged that Matt Prokop physically assaulted her and threatened her life.
Sarah filed her petition on Friday, and a hearing has been set for 10 October, to decide whether the restraining order is extended.
Her attorney Lee A. Sherman confirmed that Sarah had obtained a court order against Matt, 24, adding, "Out of respect for the court, the process and all parties, I have advised Ms Hyland not to comment on the matter."
According to TMZ, Sarah alleges in the court documents that during an argument in May, Matt became physically violent and threatened her.
During another incident, the actress is said to have sought the help of her on-screen mum Julie Bowen, who reportedly intervened at Sarah's home to help "peacefully end the relationship".
Sarah and Matt split in August after five years of dating. Following their break-up, Sarah has said he "relentlessly bombarded" her with "threatening and emotional disturbing texts and voicemails".
The former couple started dating after meeting at the auditions for High School Musical 3: Senior Year in 2008. They went on to star together in the Disney Channel film Geek Charming in 2011.