Nearly a kilometre of the shopping street was closed to vehicles on Monday, according to British media. Motor vehicles are now only allowed along the stretch at night, and then only to make deliveries to the many shops lining the street.
"It makes it much better," shopper Henry West told the BBC.
The shops and department stores on Oxford Street are visited by around half a million people every day. Mayor Sadiq Khan called it a “significant” day for the capital.
"I am incredibly pleased to see my bold vision for Oxford Street come to fruition from today," he said, according to Sky News.
Bicycles are also now banned. The ban applies between Orchard Street and Great Portland Street.