Dozens of firefighters were on the scene trying to contain the huge blaze which broke out in the outer area of the Tsukiji market.
Dozens of Tokyo firefighters were battling a blaze on Thursday at the world's largest fish market and one of the capital's most popular tourist sites, as grey smoke billowed over the city.
There were no immediate reports of injuries or people trapped, media said.
The fire broke out just before 5:00 pm, and some 44 fire trucks were on the scene. But efforts to contain the flames were hampered by the area's narrow streets and tight-knit buildings.
The cause was not immediately known.
The flames spread to five buildings covering some 300 square metres later in the evening, media said.
"I hope the area will be able to quickly recover to what it was before," said Kiyoshi Kimura, president of a company that operates the sushi chain Sushi Zanmai.
The Tsukiji "inner" market, where most seafood wholesalers are located and tuna auctions are carried out at dawn, was not affected.
Tokyo governor Yuriko Koike said the market's age and vulnerability to a big earthquake meant it had to be rebuilt.