Joining them was federal Opposition Leader Tom Mulcair, who took shots at Prime Minister Stephen Harper and Liberal Leader Justin Trudeau for what he called their shortfalls on the labour file.
He said many of the gains brought in by the labour movement — such as workplace health and safety measures and wage equality — are currently "under attack" in Canada.
Both Harper and Trudeau voted against anti-scab legislation brought forward by New Democrats, he said.
"In Toronto now, more than one half of families do not have a single, full-time steady job that they can rely on," Mulcair said.
"Under the Conservatives and the Liberals we've lost a whole generation of well-paid manufacturing jobs. We've got to get back to a situation where people can have a full-time job with a pension, enough for their family to live on."
Paul Lefebvre, former president IAMAW Local 2323, which represents 4,000 aviation workers in Ontario, said the union came out to send Ottawa a message.
"We think our country needs to have a correction in the direction its going politically and I think a lot of people feel that way and the march is getting bigger for that reason," he said.
Other labour groups at the parade, including the United Steel Workers, echoed that sentiment.
"Today is an opportunity for us to get together with all types of labour folks to look back on our strong, rich history and celebrate that — but also to re-energize for the struggles ahead," said Marty Warren of United Steel Workers District 6.