London Fire Brigade said it was called to the arena on Millennium Way, Greenwich, at about 11:15 BST.
About 21 firefighters tackled the blaze, which was contained to the restaurant's extraction system.
Station Manager Martin Freeman said: "It did create a lot of smoke and so security staff evacuated people from arena. There were no injuries."
At the time Julie Price tweeted: "At O2 for Elvis exhibition but can't go in as its on fire."
The cause of the fire is not yet known.
More than 1,200 people were evacuated from the O2 Arena in London due to a fire at a restaurant.