Hantz formerly managed Sochaux, who had a playing career before coaching. On 18 December, he was named as new head coach by Le Havre and was released after the end of his contract on 30 June 2010.
In January 2016, Hantz replaced the duo of Pascal Baills and Bruno Martini as Montpellier coach.[3] He succeeded in his mission of keeping the club in Ligue 1, with Montpellier ending the season ranking 12th for the 2015–16 season.
In January 2017, following a difficult start to the second part of the season, the hardcore supporters of Montpellier, Butte Paillade 91, demonstrated their support for Hantz by showing up at the team's training with slogans in support of the coach and speaking out in his favour.