Both teams had just pride to play for but it was Nancy who started the stronger and made early pressure tell to break the deadlock after 10 minutes.
Sebastien Puygrenier was the man to score the opener, reacting quickest to a corner kick and smashing home from close range.
Brest were unable to respond as Benoit Lesoimier missed from a tight angle and the visitors took full advantage to double their tally before the break.
Nancy captain Puygrenier made the difference once more, bundling home his second to put Nancy in complete control.
Wasteful finishing was a prominent theme in the second half but two minutes from time Brest secured a late lifeline when Charlison Benschop halved the deficit.
The hosts pushed for a late equaliser but finished a dismal season with defeat, while Nancy claimed three points, which means they missed out on survival by just a single victory.