The demonstration took place amid high unemployment and a national debt 127 percent over Italy's annual economic output -- and brought out a number of so-called radical leftists who mixed with the union members and other attendees, the BBC said.
The total turnout was not clear, the BBC said, although rally organizers had predicted a crowd of about 50,000.
The rally was aimed at the newly formed coalition government of Prime Minister Enrico Letta, a center-leftist.
The BBC said polls showed public support for Letta's coalition with the center-right was fading after only two months as Letta focuses more on property tax reform than job creation.
The demonstrators lumped Letta in with previous Italian leaders and called on him to drop the austerity policies that had been a main issue in the election.