The Canaries were paired along with Toulouse that finished third in Ligue 2 to slug it out for the Ligue 1 ticket.
Nantes hit the ground running in the encounter, with Simon setting up Ludovic Blas to open the scoring in the 10th minute of the encounter.
Nine minutes later, Deiver Machado levelled proceedings for Toulouse after receiving an assist from Vakoun Issouf Bayo.
Randal Kolo Muani then handed the lead to Nantes in the 22nd minute when he pounced on a loose ball after Mali international Kalifa Coulibaly’s effort was parried by goalkeeper Maxime Dupe.
The strike proved crucial as it ensured Antoine Kombouare’s men secured a first-leg advantage ahead of the second leg.