Four fire engines and around 25 firefighters attended a fire on Market Road in Islington.
The fire occurred at a mixed-use building. Part of a balcony of a first-floor flat was damaged by fire. One woman was assessed at the scene by the Brigade and London Ambulance Service.
The fire is believed to have been caused by the unsafe disposal of smoking materials.
A spokesperson for London Fire Brigade said: "Smoking is still one of the leading causes of fire in London.
“While we’d rather you didn’t smoke at all, if you are a smoker, it’s vital you make sure that your cigarette is completely out when you’ve finished smoking it and disposed of responsibly. If you don’t, you risk causing a fire which could not only destroy your home but also cost you your life.
“A single careless act, such as a discarded cigarette, can have devastating consequences - threatening lives, destroying multiple homes and displacing families in a matter of minutes.
“If you are smoking on a balcony, remember that non-smokers are reliant on others to put their cigarettes right out when they’ve finished them. Make sure you dispose of your smoking materials safely in an ashtray and never drop ash or throw cigarettes from balconies.
“If you’re worried about a neighbour’s cigarette setting your balcony alight, you can reduce the risk by clearing any flammable items from the area.”
The Brigade received the first of four calls about the fire at 1843 and Control Officers mobilised crews from Holloway, Islington and Kentish Town fire stations to the scene. The fire was extinguished by 1926.