Clermont shot to prominence in May when they announced Helena Costa as their new head coach, but the 36-year-old left the role last week citing personal reasons for her departure.
Diacre was immediately named as her successor, signing a two-year contract after impressing during a five-year spell as assistant coach for the women's national team.
On Monday, the 39-year-old took her first training session and spoke of her optimism about Clermont's chances for the coming season in the second tier of French football.
"I followed from afar what happened," she said at a news conference.
"I have no judgement to bear on her (Helena Costa) remarks.
"I welcome the initiative of the president, I'm the coach of Clermont and shall endeavour to do my job.
"I am delighted and very happy to be here. I want to have a journey with Clermont.
"It will not be easy but I'm especially happy because I have staff ready to work with me.
"At first, I'll just take an observer role (at training), until the weekend at least. The two friendlies scheduled this weekend will help me see things more clearly."
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