Mina Barak, 23, alleges that a ticket agent at de la Savane metro physically assaulted her after she requested being served in English on Monday.
Jean-François Lisée said he understands that some people in the English community feel that there is a lack of civility from people in the public service.
"I think Premier Marois was clear yesterday in saying in her speech that the Anglo-Quebecers are an important part of who we are, and I want to call on every Quebecer — francophone, anglophone or other — to show respect to one another," said Lisée.
"Everyone is not called on to be bilingual, of course, but everyone is called on to be civil, respectful and helpful," he said.
Both the Montreal police and the STM say the incident is under investigation.
Montreal police said they are reviewing surveillance tapes of the incident.