After the ambitious and wildly popular Portrait of a Lady on Fire shot Céline Sciamma into the arthouse stratosphere, she has returned with her fifth feature, Petite Maman, a warm and contained film whose scale is more akin to Tomboy. The mighty hype from Sciamma fans anticipating the film’s Berlinale premiere may be too much to bear for this delicate, low-key film. Of course it’s as impeccably directed and carefully structured as we’ve come to expect from Sciamma. But it’s more of a slow simmer than Portrait’s fiery blaze. Beware instantaneous hot takes: this is a modest work, one to sit with and chew over, one to look back on fondly after letting it percolate.

With Petite Maman, Sciamma returns to the topic of her first three features—childhood—now with one eye on the adult characters. We meet eight-year-old Nelly (Joséphine Sanz) in the hospital,...