Firefighters rescued two people from the water at Canada Water on Surrey Quays Road in Southwark.
A fire rescue unit crew brought one woman to dry land. She was taken to hospital by London Ambulance Service (LAS) crews.
Firefighters also assisted a man to safety from the water. He was also taken to hospital by LAS.
The Brigade was called at 2201 and the incident was over for firefighters by 2340.
Three fire engines Dockhead, Old Kent Road and New Cross fire stations and two fire rescue units from Battersea and Edmonton fire stations were at the scene.