Tavares reiterated a commitment agreed with the Italian government to boost the carmaker's output in the country to one million vehicles by the end of the decade, from around 750,000 vehicles last year.
His comments in a media briefing may ease fears about possible plant closures in Italy, in particular the Mirafiori complex in Turin, and Pomigliano, near Naples.
"To reach the one million goal ... we need all of our plants, which means, of course, there is a future for Pomigliano and Mirafiori," Tavares said after the carmaker released 2023 results.
The world's third largest automaker by revenues and the Italian government have engaged in a bitter war of words in the past month.
Prime Minister Giorgia Meloni has accused Stellantis, the country's sole major automaker, of taking France's interests into consideration over Italian ones, and described the group's birth as an "alleged" merger which "actually disguised a French takeover."
Rome approved earlier this month a new incentive scheme for auto purchases, worth 950 million euros ($1 billion) this year.
"We are so grateful to the Italian government," Tavares said, adding that Stellantis' calculations showed incentives "automatically" add 20,000 vehicles to Italy's annual automotive production.
Stellantis' brands include Fiat, Jeep, Citroen and Alfa Romeo.
The group has said the Italian output goal depended on several factors on top of incentives, including the development of an electric vehicle charging network and lower energy costs.
If Stellantis could sustain the 10% output growth it delivered in Italy last year, it could reach one million "very, very fast", before 2030, Tavares said.
But if another carmaker started producing in the country, it would made the target harder.
"If we invite more Chinese carmakers to produce in Europe, do you think it's going to help?," Tavares said.
On Wednesday, Industry Minister Adolfo Urso said Italy had been working for months to attract another carmaker to the country.
($1 = 0.9312 euros)
