2020 will mark Deletraz's fourth campaign in Formula 2, and his second with Charouz after he raced for it in 2018, where he picked up two podium finishes.
Last year, he moved to Carlin where he enjoyed his most successful season to date in the F1 junior category, finishing on the podium twice and ending the year eighth in the championship.
"I'm looking forward to working with the guys at Charouz again, many of whom are the same as when I drove there in 2018," Deletraz said.
"I know they have good experience like me so I'm confident we can put that together and do something good in 2020. I'm focused on fighting at the front and trying to win with Charouz. I will go there and do the maximum."
Deletraz is joined at the team by Pedro Piquet, the son of three-time Formula 1 world champion Nelson. Piquet is the third confirmed newcomer to the series, after Robert Shwartzman and Marcus Armstrong.
Piquet raced in the FIA Formula 3 championship in 2019, claiming one race win and a further two podium finishes to end the season fifth in the standings.
At the post-season F2 test in Abu Dhabi, Piquet tested with Charouz, which was also his first time stepping behind the wheel of an F2 car.
"After two years in GP3 and F3, the time is right to take the next step in my career and I think I'm ready for the challenge that F2 will bring," Piquet said. "I think I had some good training in the last series and that will definitely help me.
"I'm happy to join Charouz because they had two strong years in F2 and they have a fast car. One of the other reasons I decided to go there is because I know the engineering part of the team very well and I knew I would work with good people."
Team owner Antonin Charouz added: "We're very happy to welcome Louis back to the team and to bring in Pedro who impressed us when we monitored his progress in F3 last season.
"As testing showed, I think we have a driver in Louis that is capable of winning races and we believe Pedro will learn quickly and give a good account of himself as he makes an important step in his career. We're excited about what the new season could have in store for us."
Bahrain International Circuit - Winter testing