Moussa Sissoko's goal after just 11 minutes proved to be the difference as the hosts ended the game with 10 men.
Sissoko broke the deadlock with a right-footed shot from the right side of the Nancy penalty box after being sent through by Daniel Braaten.
There was little eventful action for the remainder of the first half, but things burst into life just minutes into the second period.
That gave Toulouse the initiative to find their second goal of the evening, although Nancy pressed on for the equaliser.
However, neither side failed to score thereafter and it ended 1-0 to the visitors.