Mamoudou Gassama, 22, scaled the building after seeing the four-year-old in danger.
Mr Gassama took just seconds to reach the child in a spectacular rescue captured on film and viewed by millions on social media.
The footage shows Gassama pulling himself up from balcony to balcony with his bare hands as a man on the fourth floor tries to hold on to the child by leaning across from a neighbouring balcony.
On reaching the fourth floor Mr Gassama puts one leg over the balcony before reaching out with his right arm and grabbing the child.
Firefighters arrived at the scene to find the child had already been rescued.
"Luckily, there was someone who was physically fit and who had the courage to go and get the child," a fire service spokesman told the AFP news agency.
Paris mayor Anne Hidalgo phoned Mr Gassama to thank him for his act of bravery.
"He explained to me that he had arrived from Mali a few months ago dreaming of building his life here," she said.
"I told him that his heroic act is an example to all citizens and that the city of Paris will obviously be very keen to support him in his efforts to settle in France."
Mr Gassama has been invited by French President Emmanuel Macron to the Elysee Palace on Monday to be honoured for his bravery.
Mr Gassama told reporters he acted without thinking.
"I saw all these people shouting, and cars sounding their horns. I climbed up like that and, thank God, Isaved the child,"he said.
"I felt afraid when I saved the child... (when)we went into the living room, I started to shake, I could hardly stand up, I had to sit down."
It is understood the child's parents were not at home at the time.