The march and rally, which was supported by celebrities including actress Emma Thompson, musician Peter Gabriel and UK flood victims, was one of 2,000 events taking place in 150 countries around the world ahead of a UN climate summit next week.
Upwards of 100,000 people were expected to take to the streets of New York, where the summit is being held, to demand leaders take action to tackle rising temperatures.
The UN summit has been convened by Secretary General Ban Ki-moon in a bid to drive action and momentum towards global climate treaty talks in Paris in 2015.
Thompson said: “Every single person on this earth has the power to change the world. And when we all come together, our power becomes irresistible.
“Together we have built countries and cultures and technologies. Now we must use our power to tackle the biggest threat humanity has ever faced.”
Other events around the world range from rural Papua New Guinea, where primary school students will march to a lighthouse semi-submerged due to rising sea levels, to the US-Canadian border between Vancouver and Seattle, where people will link hands to show climate change knows no borders.
And in New York, Mr Ban has said he will join marchers who are demanding “action not words” at the summit next week, which is being attended by more than 120 world leaders including Prime Minister David Cameron.
Campaign groups including Avaaz, Greenpeace UK, Christian Aid and Friends of the Earth took part in the march in London, while other events were due to take place in cities around the UK.