Renée Michel is a 54-year-old widowed concierge. She has never been to college because she considers herself to always have been poor, discreet, and of no significance. Renée, however is self-taught; she reads works of the German philosopher Immanuel Kant and Russian writer Leo Tolstoy (and even names her cat "Leo"), disdains the philosophy of Edmund Husserl, adores 17th-century Dutch paintings, likes Japanese art-house films by Yasujirō Ozu, and listens to the music of composers Henry Purcell and Gustav Mahler.
Renée, who conceals her true self to conform to the lowly image of typical concierges, introduces herself as "a widow, short, ugly, chubby", with "bunions on my feet and, on certain difficult mornings, it seems, the breath of a mammoth". Her outward appearance is summarized by The Guardian reviewer Ian Samson as "prickly and bunioned". When Paloma eventually discovers Renée's identity, she describes the latter in her journal as having the "elegance of the hedgehog"—although like the spines of the hedgehog, she is covered in quills and prickly, within, she has in the words of the English translation of the book quoted by Viv Groskop "the same simple refinement as the hedgehog: a deceptively indolent little creature, fiercely solitary—and terribly elegant".
Paloma Josse, an advanced twelve-year-old, belongs to one of the conventional families living in the posh apartment building where Renée works. Daughter of an important parliamentarian father (a former government minister), and a Flaubert-quoting mother, Paloma has a penchant for absurdism. She regards her sister's scholarship as "cold and trivial" and deems her mother's culture as conventional and useless. Paloma herself values Japanese works, and reads manga, haiku, and tanka. She keeps two diaries, one called "Journal of the Movement of the World" to record her observations of the world around her, and the other called "Profound Thoughts" to record her many and wide-ranging reflections on art, poetry, people and herself. She is introspective, and truly kind, though she tries her best to avoid the inquisition of others. She understands many facets of the world that are unseen by others, and deeply understand the way the world works, and the many perils and pitfalls of adulthood and the many hypocrisies of modern society, and therefore resolves in not an all melodramatic way, to commit suicide. However, a drastic plot twist at the end of the tale opens to her an amazing new truth: beauty, that provides meaning to our lives.
Other characters developed by Barbery in the novel include Kakuro Ozu, the cultured Japanese businessman, and Manuela, a Portuguese cleaner. Ozu, a tenant, shares Paloma's fascination with Renée's masked intelligence and brings her out of her shell (and also happens to set the entire book in forward motion), while Manuela is responsible for cleaning the apartments' toilets and is Renée's only real friend.