The debate between Rob Ford, John Tory, Olivia Chow kicked off at 7 p.m. ET.
Chow opened the debate, promising action on child poverty, transit and unemployment in her opening remarks.
"Our city is at a crossroads," she said. "We need a change of direction ... We need a mayor that will invest now. We need to invest now."
Tory focused largely on traffic and transit in his opening remarks, trumpeting his SmartTrack transit plan.
"The greatness of this city is no cause for self-congratulatory back-slapping," he said.
Ford used his opening remarks to tout his record as mayor.
"Is this city better than it was four years ago? Absolutely," Ford said.
Ford also used the opportunity to take aim at Tory's SmartTrack plan.
The transit plan is expected to be a contentious issue at tonight's debate as both Ford and Chow look to make gains with voters as Tory leads in the polls.
Toronto voters head to the polls on Oct. 27.