Gassama reportedly arrived in France a year ago, after crossing the Mediterranean and arriving in Italy.
As well as being made a French citizen, Mr Gassama will be offered a place in the fire brigade for his bravery.
Gassama told Macron during a visit on Monday that he "did not think twice" before springing into action. 'I climbed... Thank God I saved him'.
"He's truly a hero", the boy's grandmother said of Mamoudou Gassama, who climbed four floors before a crowd of well-wishers to pluck the child from danger.
Elysee Palace announced Gassama, who has been in the country for a few months, will receive French citizenship to thank him for his heroics. "We'll obviously be setting all your papers straight and if you wish it, we will start the process naturalization so that you can become French", he added.
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Paris Mayor Anne Hidalgo called the 22-year-old to thank him and later praised him on Twitter.
He simply chose to go up... he climbed all the way to the 4th floor and when he reached the kid he grabbed the kid and placed the little one with him on the balcony.
French media said the boy's parents were not at home when the incident occurred. "You need courage and the capability to do that".
In an interview with BFM TV, Gassama said once he had the boy safely in his arms, he asked him why he did that, but the child, probably in shock, did not initially reply.
Gassama, who did not seek asylum in France, making him an economic migrant at risk of deportation, has been doing odd jobs in construction.
The father was held for questioning by police for having left his child unattended. I'll just give you a moment to get to that point.
The French media reported that the father of the small child was detained for alleged parental neglect.
The boy's mother was not in Paris at the time as she was with family members in France's Réunion Island, in the Indian Ocean.