It took four engines and 21 firefighters to extinguish the blaze, which the London Fire Brigade assumes was started when a bird carried a lit cigarette to its nest.
"When we got up into the roof, we were baffled as there were no obvious ignition sources. No one had been up to there for a long time and there were no electrics that could have sparked a blaze. Neighbors told us they often saw birds flying in and out of a hole in the roof.
"We believe that one of the birds picked up a cigarette butt that was still smouldering and dropped it into the nest, causing it to catch fire and set the roof alight."
Nine human residents were forced to flee the building. The smoking pigeon and its family also appeared to have escaped unharmed.
This is the second time in two years that one of London's smoking pigeons has nearly burned down a building. Firefighters believe a fire last year began when one of the birds dropped a cigarette down a chimney.