Constance Debré is the daughter of journalist François Debré (1942-2020) and former model Maylis Ybarnégaray (1942-1988), granddaughter of Michel Debré (1912-1996), former Prime Minister of General de Gaulle, and of Jean Ybarnégaray (1883-1956), minister of the Vichy regime and resistance fighter. She is also the niece of the statesman Jean-Louis Debré.

She was 16 when her mother died. She studied at Lycée Henri-IV, then law at Panthéon-Assas University. She is a graduate of class 99 (E99) of the ESSEC Business School. Married in 1993, she had a son in 2008. A lawyer by profession in 2010, she accompanied her father in 2011, charged in the case of fictitious jobs at the town hall of Paris. Recognized for her eloquence, she was elected second secretary of the Conference of Lawyers of the Paris Bar in 2013.

In 2015, she finally left her husband and her job to live with a woman and pursue a full-time career as a writer.