A rugged, unsmiling lawyer who serves as the primary perspective for the story. He lives austerely but demonstrates leniency and loyalty toward others, often acting as the last good influence for troubled men. Driven by a dogged pursuit of truth and a concern for propriety, he takes on the role of an amateur detective to investigate his friend's mysterious beneficiary.

Dr. Jekyll is a large, smooth-faced doctor of fifty, known for his respectable nature, philanthropy, and somewhat unconventional scientific views. He holds a mysterious and highly concerning connection to Mr. Hyde, a pale, dwarfish younger man who inspires instant revulsion in those who meet him. The precise nature of the bond between the generous doctor and the cruel, impulsive younger man forms the central mystery of the narrative, especially after a troubling will designates the younger man as the doctor's sole benefactor.

A well-known man about town and distant cousin to Mr. Utterson. Despite apparent outward differences in their lifestyles, he maintains a strict weekly walking routine with his cousin, often in comfortable silence. He is a person of conscience who actively intervenes when he witnesses wrongdoing in the streets of London.

A hearty, healthy, dapper, and red-faced gentleman who runs a highly successful medical practice. He is a traditional, rationalist scientist who strictly adheres to logical deduction. This conventional approach places him at intellectual odds with his former close friends who pursue more mystical scientific theories.

An elegant, elderly former member of parliament with white hair and an innocent, old-world kindness of disposition. He is a highly respected member of the community whose sudden, senseless murder provokes public outrage and a massive police investigation.

Mr. Utterson's head clerk and a trusted confidant. He is an expert in handwriting analysis who provides crucial forensic insight into a suspicious letter, functioning as a vital resource in the ongoing investigation into the mysterious events surrounding his employer's clients.

A loyal, observant butler who has served his master for twenty years. Far from a passive servant, he is courageous and perceptive, possessing a strong sense of working-class common sense. He takes active steps when he suspects foul play in his employer's household, showing deep attachment and heroic responsibility.

A police inspector who leads the investigation into the death of an elderly member of parliament. He approaches the case with professional ambition, recognizing the public significance of the crime, and systematically searches the Soho district for the suspect.