Authorities said as many as two people broke into a money exchange business near McGill College Street.
Montreal police spokesman Raphael Bergeron said only one employee was working when the suspect or suspects broke in.
"One or two suspects broke into the business by a wall that was separating the money exchange business with an empty business on the side, so she got surprised by the suspects," Bergeron said. "Then, basically, she was tied up."
The woman was treated for shock but was not hurt.
Authorities say it is unclear how much money was taken.