Ten fire engines and around 70 firefighters dealt with flooding in the area around Canonbury Street in Islington.
A 36-inch burst water main caused flooding up to a depth of around 44cm of water. This affected properties on Canonbury Street, Essex Road, Elmore Street, Halliford Street and Ecclesbourne Road.
Around 30 residents were evacuated from their homes to a rest centre as crews worked alongside Thames Water, the local council, and the Metropolitan Police Service to support affected people and make the scene safe.
Firefighters used flood barriers and sandbags to divert flood water away from homes.
Disruption is likely to continue throughout the morning and the public were urged to avoid the area and not to attempt to drive through flood water.
The Brigade's Control Officers took the first of 23 calls to the incident at 2204 and mobilised crews from Islington, Stoke Newington, Holloway, Euston and surrounding fire stations to the scene. The incident was over for firefighters by 0235.