Police fired tear gas when some among the estimated 2,000-3,000 marchers pelted international peacekeepers with stones, but the rally was for the most part peaceful.
It was just the latest in a series of large-scale demonstrations by the opposition in Haiti, the poorest country in the Americas, ahead of the runoff election scheduled for December 27.
The October 25 first-round vote was the latest attempt to shed chronic political instability and work toward development, but instead it has only heralded yet more protests and unrest.
The runoff will be between Jovenel Moise, backed by the outgoing president and the ruling party, and Jude Celestin, one of the more than 50 opposition candidates.
Moise won 32.8 percent of the vote and Celestin took 25.3 percent, but the opposition has alleged vote fraud, while also denouncing what it perceives to be the interference of the international community.