"It's loud, lively and people are dancing in the streets," one of the organisers Michael Williams told Sky News. "It's a great day out for the family."
More than 300 food stalls sold traditional Caribbean dishes such as curried goat, spicy barbecued "jerk chicken" and Jamaican rice and peas.
Organisers said the crowds will munch their way through five tons of chicken and 16,000 coconuts, washed down by 10,000 litres of stout and 25,000 bottles of rum.
Before the carnival got under way, police arrested 21 people suspected of planning to cause trouble at the event. Four more were arrested on Sunday, three for drugs offences and one for criminal damage.
Police are taking no chances after a spate of teenage killings in the capital this year.
"We will do all we can to stop the small minority from spoiling this vibrant event for the thousands who enjoy it every year," said Deputy Assistant Commissioner Chris Allison, of the Metropolitan Police.
