Matthias Schoenaerts was François Ozon's original choice for the role of David/Virginia, but the actor turned it down. Schoenaerts was filming Far from the Madding Crowd (2015) at the same time that "The New Girlfriend" was being filmed. Romain Duris was cast instead.
When baby Lucie is being fed by bottle, a kind of little toy radio is playing. The attentive listener will recognize a fragment of the Goldberg Variations (BWV 988) by J.S. Bach.
At the start of the film Laura wears a Gerbe Sunlight 15 denier stockings, given by it's distinctive lace welts.