The latest victim to die was diagnosed before Aug. 29 and died Monday, officials said.
Authorities say the outbreak is under control with no recent new cases, the Canadian Broadcasting Corp. reported. Some patients were still in intensive care units, however.
The CBC said 176 people have fallen ill with Legionnaires' since the outbreak started in July.
"At this time, what we say is the outbreak is under control, because we don't have new cases with the beginning of the disease after Aug. 29," said Dr. Francois Desbiens, director of public health.
Building cooling towers have been found to be prime areas for the Legionnaires' bacteria to thrive. Quebec City officials have inspected and disinfected 130 cooling towers across the city.
Building owners have been directed to maintain a minimum level of chlorine in the cooling towers' water at all times.