Klara is a B2 model Artificial Friend (AF) designed to provide companionship for teenagers. She is uniquely observant, constantly analyzing the emotional cues of the humans around her with a grid-like visual processing system. Powered by solar energy, she holds a deep, reverent fascination with the Sun, believing it possesses omnipotent healing powers. Her primary drive is to prevent loneliness in her chosen human companion, leading her to make elaborate plans based on her limited understanding of the physical world.

Josie is a teenager who selects Klara to be her Artificial Friend. She has undergone a genetic enhancement procedure known as being "lifted," which has left her suffering from a severe, unexplained illness. Despite her precarious physical health, she maintains a warm demeanor and tries to shield her mother from worry. She frequently struggles with the social expectations placed upon her by her wealthy, genetically enhanced peers.

Chrissy is Josie’s mother, a working attorney fiercely determined to secure her daughter's survival and social standing. She carries a heavy burden of grief from the loss of her older daughter, Sal, and experiences intense anxiety over Josie's declining health. Her interactions are often erratic, shifting quickly from warm vulnerability to harsh, demanding behavior.

Rick is Josie’s closest friend and neighbor. Unlike Josie, he is "unlifted" (not genetically engineered), which severely limits his educational and professional prospects in their highly stratified society. He is intelligent and talented at engineering drones, though he feels out of place among Josie's wealthy, enhanced peers.

Mr. Capaldi is a scientist and artist commissioned by Chrissy for a specialized portrait project involving Josie. He represents the cold, rationalist side of the novel's dystopian society, advocating for technological solutions to human grief. He is outwardly polite but dismissive of emotional attachments, arguing that reservations against his work are merely sentimental.

Helen is Rick’s mother, an Englishwoman who struggles with the social and financial consequences of choosing not to have her son genetically enhanced. She carries immense guilt over how this decision has limited Rick's future and desperately searches for ways to secure his entry into Atlas Brookings, an elite university.

Paul is Josie’s father and Chrissy’s ex-husband. He is a talented former engineer who was "substituted" out of his profession, leading him to live in a segregated community of similarly displaced former professionals. He remains deeply concerned about his daughter's health and views the scientific solutions proposed by others with open skepticism.

Manager is the caretaker and supervisor of the Artificial Friends in the store where Klara begins her life. She is observant and kind, acting as a pragmatic maternal figure to the androids before they are purchased.

Melania is the housekeeper for Chrissy and Josie. She monitors the household closely and initially views Klara with heavy suspicion, carefully tracking the android's interactions with the sick teenager.

Rosa is a B2 model Artificial Friend and Klara's companion in the store. Unlike Klara, Rosa is not particularly observant of the complexities of the outside world, often misinterpreting the human behavior she sees through the window.

Vance is an ex-boyfriend of Helen's who currently serves on the scholarship board at Atlas Brookings, a university that admits unlifted students. He harbors long-standing resentment over his past relationship with Helen.

Sal is Josie’s older sister, who passed away from the same illness currently afflicting Josie. Her death casts a long shadow over the family, deeply influencing Chrissy's actions and anxieties.

A celestial body that Klara worships as a sentient, divine being. Because she is solar-powered, she believes the Sun provides a special nourishment that can heal sickness and influence earthly events.