Benoit Jacquot, 77, and Jacques Doillon, 80, spent the night at a Paris police station after being summoned for questioning on Monday morning, and have denied all charges.
Their interrogation over the alleged abuse of much younger actors, including in the 1980s and in several instances when they were underage, comes as activists say French cinema has too long provided cover for abuse.
Investigators opened a probe after actor and director Judith Godreche, 52, earlier this year officially accused Jacquot of rape during a relationship with him that started when she was 14 and he was 25 years her senior.
She also filed a complaint against Doillon over sexual assault during a film shoot when she was 15.
Several other actors have since come forward with similar allegations.
Isild Le Besco, 41, has filed a complaint over rape during a relationship with Jacquot that also started when she was underage, and Julia Roy, 34, has accused him of sexual assault.
Le Besco has also claimed Doillon made advances during work sessions, while Anna Mouglalis, 46, alleged the filmmaker forcefully kissed her in 2011.
Jacquot and Doillon's lawyers have objected to their clients being detained for questioning, saying they could have answered questions as free men, and stressed they remained innocent until proven guilty.
They could be held for up to 48 hours from their initial detention from Monday morning.
Since breaking her silence, Godreche has become a leading voice in France's #MeToo movement.
After she appealed for a cinema oversight body, French lawmakers in May voted to create a commission to investigate sexual and gender-based violence in the film industry and other cultural sectors.
The head of France's top cinema institution, Dominique Boutonnat, stepped down on Friday after he was convicted of sexually assaulting his godson in 2020.
Boutonnat was given a three-year prison sentence, two of them suspended. He will be able to serve his one-year jail term at home wearing an electronic bracelet.
And cinema legend Gerard Depardieu, 75, put his career on hold last autumn after a string of accusations against him, all of which he denies.
He is to stand trial in October for sexually assaulting two women, and also risks a second trial after he was charged in 2020 with the rape of an actor in 2018 when she was 22 and anorexic.
