Fernandez raced in the championship for Campos Racing last year, but only one of its drivers – Alex Peroni, who ended the season early after a huge crash at Monza – scored points.
After a best finish of 12th, Fernandez finished 28th in the final standings. He did show improved pace in the non-championship race at Macau and in the post-season FIA F3 test at Valencia, where he switched to ART.
“I am very excited and grateful for the opportunity to work with a team which has such a strong trajectory for the 2020 season,” said Fernandez, who also took a podium in the Formula Renault Eurocup last season.
“I have already worked with them at the Macau GP and the Valencia tests, where I felt really good. With a team like ART Grand Prix I believe together we can achieve some very good results in the upcoming season.”
ART team principal Sebastien Philippe added: “Sebastian is only 19 years old but he already has a vast experience in motorsport and in particular, F3. This experience is a major asset in such a cutting-edge championship.
“His first appearance in Macau was solid, he made progress all weekend. During the Valencia tests, he showed the team that he listens well and that he can work diligently with all the members of the team to make the best of his skills.
“In 2020, he will have all he needs to be regularly in the points and fighting with the front runners.”
ART finished third in the FIA F3 standings last season, as it struggled to match championship dominators Prema Racing and its closest rival Hitech Grand Prix.
The team has already signed German F4 champion Theo Pourchaire and SMP Racing-backed Alexander Smolyar in FIA F3 for 2020.