Organizers claim more than 230,000, much more than had expected, rallied in the afternoon march in the Kowloon area, where most mainland Chinese tourists arrive and shop.
Hong Kong police said there were far fewer protesters, putting the number at about 56,000 at its peak.
Whatever the crowd size, many of the protesters wore black T-shirts and were holding up signs and boards that read “Rise up, Hong Kong,” “No Extradition Bill” and “No rioters, Only despotic rule.”
Some waved British flags, a nod to the territory's rulers before China.
The extradition bill is currently suspended after weeks of protests, but people were calling for a complete withdrawal of the hated legislation, which would allow transfer of fugitives to the mainland and other jurisdictions with which Hong Kong has no extradition deal.
“The government only suspended the deal. That means it could be brought up again to the legislature anytime. We don’t want to be subject to Chinese law and that’s why we are so angry,” said Holly Ho, a student, told ABC News.
A protester said the bill would create "horror."
"If the Chinese government decides to target someone, they could easily create a situation to get any one of us arrested," the protester, a man who didn't want to be identified, told ABC News. "We march now peacefully, but if that bill passes none of us would be alive.”
Hong Kong has been besieged by protests for the past month, sparked by the extradition bill and general dissatisfaction with local politicians.
Hong Kong leader Carrie Lam suspended the bill and apologized for how it was handled, but protesters want it to be formally withdrawn and for Lam to resign.
March organizer Ventus Lau said the purpose of Sunday's protest was twofold: to reiterate the protesters' demands to the government and to give mainland visitors a firsthand look at their movement.
"The information is rather blocked in mainland," he said. "We want to show them the true image and the message of Hong Kongers."
The march was the first major protest since last Monday, when protesters smashed thick glass walls to break into the city's legislature building and wreaked havoc inside, spray painting slogans on the walls, overturning furniture and damaging voting and fire prevention systems.