Firefighters were called to a burst water main on Northdown Street in Islington.
The basements in a range of terraced houses were affected by flooding from a burst water main outside. They were flooded to a depth of around a metre.
Twelve people left the properties before the Brigade arrived. There were no reports of any injuries.
Firefighters worked to pump the water out of the houses.
The Brigade was called at 1514 and the incident was over for firefighters by 1725. Four fire engines and around 25 firefighters from Euston, Islington, Shoreditch and Soho fire stations were at the scene.