Organizers of the march in Sao Paulo, which is Brazil's biggest city and financial capital, said about 30,000 people joined in late yesterday, while police estimated 17,000.
Many of them marched on the headquarters of TV Globo, that popular television station that Rousseff sympathizers accuse of being partisan and pushing for the president's ouster.
Brazil is in its worst recession in decades and a sprawling corruption scandal at the state-run oil giant Petrobras has been moving closer to Rousseff's inner circle in recent weeks.