Nightbitch is a frustrated, exhausted stay-at-home mother living in a Midwestern American town. Having previously worked as the director of a community art gallery, she left her career to care for her two-year-old son full-time when the emotional strain of daycare became intolerable. She struggles heavily with the sheer monotony of domestic life, chronic sleep deprivation, and intense isolation. Her physical and psychological state begins to fracture as she notices canine traits emerging in her body, prompting an artistic and emotional awakening.

An engineer whose demanding career takes him away from home throughout the week, returning only on weekends. He is highly rational, pragmatic, and heavily reliant on scientific logic, which blinds him to his wife's deep emotional and psychological struggles. Though well-meaning, he treats his phone conversations with her as a chore and rarely assumes a fair share of the domestic childcare load.

Nightbitch's two-year-old child, who dictates the structure and flow of her entire existence. He is an energetic, demanding toddler who requires constant attention and adherence to strict routines. He strongly resists potty training and falling asleep independently, which serves as a major source of stress for his mother.

A seemingly perfect suburban mother whom Nightbitch privately dubs "the Big Blonde." She embodies everything Nightbitch dislikes about conventional parenting, constantly smiling, joining in, and organizing community activities. She runs an herb-selling business and aggressively attempts to recruit other local mothers into her commercial network.

An academic researcher in the philosophy department at the University of Sacramento. She wrote a book detailing her search for mythical, animalistic women across different global cultures. Her writing provides context for the bizarre physical and emotional changes happening in the protagonist's life.

A woman who previously worked alongside Nightbitch at the community art gallery. She represents Nightbitch's lost professional life and the local art scene she abandoned. During their brief interaction, she forces Nightbitch to confront the vast gap between her inner turmoil and the happy facade she presents to society.

The protagonist's mother, who once harbored serious dreams of becoming a professional opera singer. She had the rare opportunity to study at a vocal school in Europe but ultimately sacrificed these ambitions when she had a child. Her life choices cast a long shadow over her daughter's current anxieties about career and identity.