The Argentine, who arrived at Stadio Artemio Franchi from Villarreal in 2012, has made 68 Serie A appearances during his two seasons at the club, contributing 10 goals.
Rodriguez's deal was set to run out in 2015, but he has now declared his delight at having resolved his future.
"I am very happy and there were never problems negotiating the renewal, so it was easy to sign the new contract," he said.
"We need to improve, even if other teams have great players, as we want to win something this season. We’ve got important players too.
"What are my objectives? I always say to win a trophy, whether it’s the Coppa Italia or the Europa League.
"Of course, getting a place in the Champions League would also be wonderful."
Fiorentina finished fourth in the Italian top flight last season to secure a European berth.
