The STC's production of King Lear, at which an altercation between usher and patron is alleged to have taken place.
The Media, Entertainment & Arts Alliance will take the Sydney Theatre Company to the Fair Work Commission over claims that the STC is prioritising commercial interests over staff safety.
The MEAA claims that ushers at the STC have been assaulted by patrons in two recent incidents.
MEAA director of Entertainment, Crew and Sport Mal Tulloch said the incidents had left staff feeling violated, humiliated and isolated.
In the first incident, the union alleges, an usher was forcibly pushed by a patron during a performance of King Lear.
The MEAA claim the second incident involved a member being forcefully slapped on the back a number of times and then subjected to an offensive gesture.
In both occurrences, staff had followed the STC procedures, and had done nothing to provoke the incidents, the union said.
The MEAA claims that one of the perpetrators was a season ticket holder and a well-known patron to the STC.
STC management had accepted an apology and allowed the patron in question to return to the premises, the MEAA said.
Mr Tulloch said the MEAA has demanded the patron be barred from the venue indefinitely.
He said the employees affected have been discouraged from making formal complaints and management has rejected an offer from the union to work together to develop new health and safety procedures for similar incidents.
“There is no excuse for violence in the workplace,” Mr Tulloch said.
“There has been inadequate consultation from management to determine a safeguard for our members and our efforts to see better procedures for dealing with violent patrons have been ignored by the STC.
“We are appalled and alarmed that STC is willing to put a paying patron’s bad behavior above the safety of its staff.”
The STC told Fairfax that the company disputed the characterisation of the first incident as an assault, and is actively investigating the second.