Toulouse kept themselves in the hunt for a Champions League place next season thanks to Andre-Pierre Gignac's classy strike.
France international Gignac scored his 19th goal of the season early in the second half, sending Toulouse up two places to fourth in Ligue 1.
Nantes dropped into the bottom three with the defeat but they had the best early efforts at goal.
Their first big opportunity came in the 23rd minute when Guirane N'Daw's free-kick came to William Vainqueur and his volley from 18 yards flew wide.
Another came 11 minutes later when Remi Mareval took a free-kick and, seeing goalkeeper Cedric Carrasso off his line, looked to float the ball into the empty net.
Carrasso got back quickly though, to preserve the goalless deadlock.
Toulouse threatened just four minutes before half-time when Etienne Braaten's corner picked out Jeremy Mathieu whose header went just wide to the right of goal.
The home side went ahead after 52 minutes when the newly-capped Gignac maintained his prolific form.
Etienne Didot played the ball to Braaten who surged past a Nantes defender before offloading a pass to Gignac, whose firm shot from the edge of the penalty area found the net off a post.
Toulouse then had a spell of bossing the game and Didot's free-kick from long range deflected off Mathieu and almost deceived goalkeeper Jerome Alonzo. The ball hit Alonzo on the chest and bounced against the bar before going out of play.
Mathieu then saw his free-kick in the 72nd minute deflect wide off Jean-Jacques Pierre, while seven minutes later Alonzo blocked Fode Mansare's shot from the edge of the penalty area.
Nantes stayed just one goal behind though and could have equalised in the 90th minute when Djamel Abdoun's strike from the edge of the penalty area forced Carrasso to make a decisive save.