A lawyer for the actress, who plays Haley Dunphy in the sitcom, has said she obtained a court order on Friday, 19 September.
The domestic violence temporary restraining order came a month after Sarah and Matt ended their five-year relationship.
Sarah's lawyer has issued a statement saying: "Out of respect for the court, the process and all parties, I have advised Ms Hyland not to comment on the matter. We request that you respect the parties' privacy during this time."
An rep for Matt has made no public comment yet.
Sarah, 23, and Matt, 24, met during an audition for High School Musical and went on to star together in Disney movie Geek Charming.
They had been living together in LA before their separation.
TMZ and several US outlets claim that court documents reveal Sarah's Modern Family onscreen mum Julie Bowen (Claire Dunphy) stepped in to help her end the relationship.
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