The left-back, 20, is now travelling to Tyneside in order to finalise his move to Alan Pardew's side. French media report the deal is worth 3.5 million euros (£2.9m).
A Nancy statement read: "After 46 games and two-and-a-half years in the Nancy shirt, Massaido Haidara is leaving his former club for Newcastle United, currently 16th in the Premier League.
"The two clubs have reached an agreement and will finalise the transfer on Tuesday."
Haidara made his debut for Nancy in the 2010-11 season and was recently linked with a possible move to Serie A side Fiorentina.
The full-back will become the seventh Frenchman in Pardew's squad and could soon be joined by an eighth, with Montpellier defender Mapou Yanga-Mbiwa expected to conclude his move to St James' Park soon.
The France international has been criticised for his decision to join Newcastle though.
Montpellier president Louis Nicollin said: "He chose Newcastle? If so, he is an ass. It is not my fault but I think the manager [Alan Pardew] played a role. Newcastle, this is really not a good choice. They will transfer him the next year.
"It doesn't bother me. We're not going to cry. He is not irreplaceable. The important thing is that we get money."