"On Tuesday morning Pablo Correa will lead his first training session," the club said on their website.
Correa was coach of AS Nancy between 2002 and 2011 and named manager of the year in 2006 and 2007.
Former Marseille defender Casoni, whose contract was due to run out in June, led Evian to two successive promotions to reach the top flight for the first time. Evian are 11th in Ligue 1.
"Evian Thonon Gaillard and Mr Casoni mutually agreed on this day to cease working together," the club added.