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.
That led to reported interest from Roma, although a move never materialised, with the forward scoring four goals in all competitions this term despite struggling with injury.
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."
