The former France international has taken charge of the Ligue 2 side after previously working as assistant for the women's national team
The Stade Gabriel Montpied side were in the market for a new boss following previous coach Helena Costa's decision to resign just one day after she was officially presented as the new woman in charge.
Costa accused Clermont of amateurism and disrespectful behaviour, saying she was not kept in the loop over possible signings and the club's pre-season schedule, leaving her with no other choice but to step down.
The 39-year-old Diacre played her entire active career for Sochaux and made over 100 appearances for the France national team before hanging up her boots in 2006 due to a knee injury.
Diacre has previously been at the helm of Sochaux's female side and was assistant to Bruno Bini for France's female national team.
She became the first female to obtain the necessary papers to coach in Ligue 1 and Ligue 2 earlier this year and now becomes the first woman to take charge of a professional club in the top two tiers of any European league in the men's game.