The Italian has been with Ducati since joining from Tech 3 Yamaha at the beginning of the 2013 season.
Dovizioso, whose solitary win in MotoGP came while he was riding for Repsol Honda, finished eighth in the standings last year.
He lies fourth in the current campaign, having made the podium in Texas and Assen.
"We've reached an agreement and this is because it's an interesting project which is beginning to bear fruit with the arrival of [general manager Luigi] Dall'Igna," Dovizioso said.
"We've had two podiums already this season and we are fourth in the World Championship.
"The current situation is really exciting, especially with the plans for 2015 in mind."
Ducati motor holding director Claudio Domenicali added: "Andrea has been with us for two years now and has shown his belief in this project. After a difficult 2013 he has given us two podiums this year. He is our best rider."