TMZ reports that the 29-year-old man grabbed the actress's breast as she was posing for photos with fans. He was arrested outside the event after the occurrence.
The 23-year-old star reportedly left the party in tears after the incident. She apologized to her fans for leaving early on Wednesday via Twitter.
"Sorry to all the fans outside the #qantas event that I didn't get to say hi to but I had to leave due to an inappropriate touch of a fan," Hyland wrote.