Varjak is a Mesopotamian Blue cat with silver-blue fur and amber eyes. Because the rest of his family has green eyes and prefers a sheltered life indoors, Varjak feels isolated and out of place. He possesses a deep instinct for adventure and loves listening to tales of his ancestors. When a mysterious threat enters his home, he must overcome his fears and venture into the unknown city.

Jalal is Varjak's legendary ancestor, a famed explorer and hunter who originally traveled from Mesopotamia to London. He appears as an old cat with silver-blue fur and amber eyes. As a strict but wise teacher, he instructs Varjak in a secret set of martial arts and survival skills known as the Way of Jalal.

Holly is a spiky-furred, black-and-white street cat with mustard-colored eyes. She survives the harsh conditions of the city through careful observation and resourcefulness. Though initially guarded and cynical about the value of friendship, she proves to be highly capable and deeply loyal to those she trusts.

The Gentleman is a tall, physically imposing human who arrives at the Contessa's estate after she falls ill. He wears shiny black shoes and possesses large, white hands. He uses gifts of caviar and lifelike toys to win the trust of the Paw family, though his quiet, controlling demeanor terrifies Varjak.

Julius is Varjak's older brother, a physically large and muscular Mesopotamian Blue. He relies on intimidation to assert dominance within the household and desires to be the undisputed head of the family. He is self-absorbed and quick to dismiss any potential threats to their comfortable lifestyle.

Cludge is an enormous, black, bristly dog with pointed yellow teeth. Because cats generally fear him based on old tales and his fearsome appearance, he suffers from intense isolation. Despite his terrifying exterior, he is deeply gentle and desperate for companionship.

The Elder Paw is Varjak's grandfather and the patriarch of the family at the beginning of the story. He is the only living relative who remembers fragments of the Way of Jalal. When danger arrives at the Contessa's house, he takes decisive action and entrusts Varjak with a crucial mission.

Tam is a brown street cat who wanders the city with Holly. She struggles with hunting and is deeply fearful of the city's powerful feline gangs, particularly Sally Bones. Her constant hunger often drives her to take risks in search of food.

Ginger is a massive, muscular tomcat who leads a gang controlling the east side of the city. He violently protects his territory and aggressively interrogates outsiders about the recent string of mysterious cat disappearances.

Sally Bones is a gaunt, one-eyed white cat who rules the west side of the city. Street cats whisper that she possesses supernatural powers, making her a feared figure across the urban landscape. She leads a brutal gang and enforces strict obedience among her ranks.

Razor is a striped, heavily scarred tomcat who serves as a lieutenant in Sally Bones's gang. He uses intimidation to recruit unaligned street cats and readily employs violence against anyone who defies him or his leader.

Father is a pampered Mesopotamian Blue who insists his family adhere strictly to the behaviors expected of pedigree pets. He is deeply invested in the luxury provided by human caretakers and reacts with hostility whenever his authority or comfort is threatened.

Mother is a pristine Mesopotamian Blue cat living in the Contessa's house. She focuses heavily on appearances and proper grooming, expecting her offspring to act like dignified pedigree pets at all times.

Aunt Juni is an adult Mesopotamian Blue who firmly believes the Contessa's house provides everything a cat could ever need. She actively ignores any signs of danger from the outside world and embraces a life of total complacency.