There have been several serious stabbings and other incidents of violence at the Notting Hill Carnival, police said.
The Section 60 Order was in place in and around the 9.24pm festival area and will last until 1am.
It allows a police officer to stop and search someone without being suspicious.
It took place on the last day of the west London carnival, which was enjoy the first year since the pandemic.
Nearly a million people turned up for the Adult Day event on Monday, when the streets were once again filled with an explosion of sound systems and dancers in extravagant costumes.
Police earlier said there had been 76 arrests for “various crimes” as of 7am on Monday.
A police horse also died on duty after collapsing around 9pm on Sunday.
There was 72 seconds of silence on Monday afternoon to mark the 72 people killed in a fire in nearby Grenfell Tower – one of many gestures held over the weekend to remember the tragedy.
The Notting Hill carnival celebrates Caribbean culture and is Europe’s largest street party, second only in size to the carnival in Rio de Janeiro in Brazil.
The 2020 Masquerade Festival was canceled because of COVID, although there were livestreamed events, and last year’s event was also scrapped due to the coronavirus risk.
