The tracks were part of a stack of master recordings cleared out of the basement of Polydor records in the 1960s.
Universal Music, which owns Polydor, had the masters transferred to CD and plans to release them to mark the 40th anniversary of Piaf’s death in October this year.
The tracks were bought by the National Library over 30 years ago but were left to languish before being transferred to the library's new home in eastern Paris when it opened in 1996.
The songs were uncovered by music specialists Eric Didi and Marc Monneray.
Didi says the songs were probably ones that were not considered good enough to be included on an album.
“Piaf was very demanding of herself, which probably explains why this treasure was never uncovered.”
The library was a project of the late former president, Francois Mitterand.
One of the songs, La Fille de Joie est Triste (The Party Girl is Sad) appears to be an early version of the well-known Piaf number, Accordeoniste.
Other titles include Je ne Veux Plus Faire la Vaisselle (I Don’t Want to do the Washing Up Anymore), C’Etait si Bon (It Was So Good), Ces Mains (These Hands) and La Valse de Paris (The Paris Waltz), all recorded in 1943.
Piaf’s most famous songs are La vie en Rose and Non, Je ne Regrette Rien.
She was born on December 19, 1915, in Paris and was abandoned by her mother two months later.
The singer joined her father’s circus at a young age and was later spotted by an impresario
She went on to become a hugely successful singer, despite her tempestuous private life and alcohol addiction.
In 1963, Piaf recorded her last song, L’Homme de Berlin. She died on October 11 that year.