Police say 30 people were arrested at "May Day" rallies around the city.
Protesters came out in support of equal rights for immigrants, women and workers. They say all three groups are under attack by the Trump administration.
Mayor Bill de Blasio spoke at a rally in Washington Square Park. He said Trump is purposefully trying to demonize immigrants and minorities.
"He's trying to make them blame immigrants for their economic circumstance," de Blasio said. "Guess what? The immigrants didn't create the way our economy is. The 1 percent did it. The millionaires and billionaires did it."
"Now, it's more of a fear for immigrants, and there's more of an attack on women, so everybody needs to be in solidarity, and I think that has happened a lot more now," said one attendee.
Similar events were also held around the country and the world.
In Paris, a number of hooded protesters disrupted a peaceful march by throwing molotov cocktails at police.