Thousands of people lined the Royal Docks to cheer on dozens of dragon boats racing down the Thames.
The regatta is part of a celebration of Chinese culture in the capital, raising money for local charities.
London Hong Kong Dragon Boat Festival is organised as a fund-raiser with proceeds donated to nominated charities supported by London Chinatown Lions Club.
Hans Hung of London Chinatown Lions Club said, "The 21st London Hong Kong Dragon Boat Festival promises to be a very special one-day sporting event as well as a great day out for all the family. We have 7.5 hours of racing with a mixture of amateur and professional teams competing for 4 cups and the overall winner's trophy. We also have a fantastic line up of entertainment featuring bands and artists on the East West Festival stage, plus a broad range of martial arts demonstrations. There is also a South Eastern food festival with for something for all tastes."