The 30-year-old had been heavily linked with a return to Mexico in recent days and the Ligue 1 club confirmed his departure on Wednesday.
Formerly of Ajax and Boca Juniors, Cvitanich fired 19 league goals in his opening campaign in the French top flight and made a flying start to the last campaign.
Nice thanked the striker for his efforts at the Allianz Riviera.
"It's official. Dario Cvitanich leaves OGC Nice after two and a half seasons and 36 goals in the red and black shirt in all competitions," read a statement on the club's official website.
"A transfer was made with the Mexican Pachuca club with whom he won the League CONCACAF Champions [League] in 2010.
"He will remain forever in the heart of Nice... a true scorer with a crazy charisma."
