The 19-year-old German racer, who had a breakthrough race-winning Ginetta Junior campaign in 2015 and has three podiums to her name from a subsequent two-year stint in ADAC Formula 4, has spent the past season representing Van Amersfoort racing in the new Formula Regional European Championship - where she finished seventh.
Also in 2019, she drove FIA F3-spec machinery in the Macau Grand Prix - a year on from her huge high-speed accident in the same event - for HWA, and targeted joining the outfit's full-season roster in 2020.
But while HWA ultimately filled its three F3 seats with the returning Jake Hughes, Ferrari protege Enzo Fittipaldi and Red Bull junior Jack Doohan, Floersch will now join Alex Peroni and Alessio Deledda at Campos.
"I am very happy to be competing in the FIA F3 Championship together with Campos Racing," Floersch said. "It is going to be my first season in the actual Formula 3 car with Pirelli tyres, DRS and the Mecachrome engine.
"Without any [prior] test days I have to learn a lot but I am looking forward to competing against the best drivers. For me it’s important to get better each race weekend, work together with the team and have fun."
Floersch had been previously named as part of the Richard Mille Racing Europeans Le Mans Series crew, alongside Katherine Legge and Tatiana Calderon.There are three clashes between the six-round ELMS calendar and the nine-round FIA F3 schedule in 2020.
"It is a great privilege to have Sophia in our ranks," team owner Adrian Campos said.
"She is one of the most talented drivers and a true example of perseverance. Sophia will keep fighting to continue making progress in one of the toughest championships on the international scene."
2020 FIA F3 grid so far:
ART Grand Prix