The fire erupted overnight in a small hotel in the Al-Mosky neighbourhood, not far from the Al-Azhar mosque, and moved rapidly to four nearby buildings, police told AFP.
The buildings included warehouses containing plastic materials which helped the fire to spread.
The cause of the blaze was not immediately known.
By midday it had been brought under control, Cairo fire chief Gamal Halawa said, adding that 16 firefighters and police had suffered from smoke inhalation.