Four fire engines and around 25 firefighters tackled a fire at a house converted into flats on Leander Road in Brixton.
Part of a communal kitchen on the first floor was damaged by the fire. Firefighters led four people to safety and two people were taken to hospital by London Ambulance Service.
The Brigade was called at 0303 and Control Officers mobilised crews from Brixton, Clapham and West Norwood fire stations to the scene. The fire was extinguished by 0405.
The fire is believed to have been accidental and was caused by a combustible item left too close to a heat source.