In a landmark day for the sport, 40-year-old Diacre oversaw Clermont's season-opening 2-1 defeat at Brest in Ligue 2 on Monday.
Diacre - a replacement for Helena Costa after the Portuguese woman quit before coaching a game in June - is the first woman to coach in the highest two divisions of any professional football league in Europe.
Carolina Morace was appointed coach of Italian third-tier club Viterbese in 1999 before she resigned after two matches due to heavy media pressure.
Diacre's first fixture on the sidelines in the French second division got off to the perfect start when Souleymane Sawadogo gave Clermont an eighth-minute lead at the Stade Francis-Le Ble.
But that is as good as it got for the former France women's national team assistant, as Brest scored two unanswered goals in the second half through Bruno Grougi and Alexandre Alphonse.
"It's never nice to lose, that's obvious," Diacre said. "But Brest played well. We made a couple of mistakes for their goals.
"But we did good things too, which is a good sign for the future. You can't ignore Clermont this season."Diacre added: "We didn't know how to keep the ball today - that was one of our weaknesses.
"We didn't use the ball well, we didn't develop our game as we could have, as we should have. That's what put us in danger.
"There are plenty of positive things. I have a young team and I'm happy with my players because they gave everything."
Clermont, who finished 14th last season, are back in action on Friday as they host Auxerre.