Violet is a fourteen-year-old girl with a sharp, inventive mind. When facing a mechanical problem, she ties her hair back to keep it out of her eyes and builds useful devices from everyday items. Following the sudden death of her parents, she assumes a protective leadership position over her younger siblings. She operates logically and bravely, constantly searching for a way to improve their dismal living situation under their new guardian.

Klaus is a twelve-year-old boy who wears glasses and loves reading above all else. Having spent much of his childhood in his parents' vast home library, he retains a wealth of knowledge on subjects ranging from wolves to biology. When placed in a dangerous environment, he uses his sharp memory and research skills to seek out legal rulings and historical facts that might provide his family an escape route.

Sunny is a small infant whose primary form of communication consists of high-pitched shrieks that her older siblings perfectly understand. Barely larger than a boot, she makes up for her small stature with four incredibly sharp teeth that she uses to bite things she likes. She is the most physically vulnerable member of the family, which makes her an easy target for threats and heightens her siblings' protective instincts.

Count Olaf is a tall, extremely thin man who wears soiled clothes, sports a single long eyebrow, and bears an eyeball tattoo on his ankle. A distant relative of the orphans and the leader of a shabby theatrical troupe, he takes custody of the children to steal their massive inheritance. He provides them with only a single bed, forces them to perform grueling manual labor, and treats them with open hostility and physical violence.

Mr. Poe is a banker at Mulctuary Money Management and a former friend of the orphans' deceased parents. Tasked with executing the estate and finding a relative to raise the children, he operates strictly by bureaucratic rules. He frequently coughs into a white handkerchief and dismisses the children's desperate pleas for help, incorrectly trusting that their new guardian's legal authority means they are safe.

Justice Strauss is a High Court judge who lives in a beautiful, clean house neighboring the antagonist's crumbling mansion. She takes a quick liking to the orphans and kindly allows them access to her massive private library. Despite her genuine warmth, she adheres strictly to legal customs and fails to recognize the severe danger the children face right next door.

Lemony Snicket is the melancholic narrator documenting the unfortunate events of the orphans. He frequently pauses his storytelling to define words for the reader, often using cynical or humorous examples to clarify a point. He views it as his solemn duty to record these tragic events and transmit them to his publisher, even though investigating the sad story brings him personal distress.

The Hook-Handed Man is a menacing assistant in the theatrical troupe whose hands have been replaced by sharp metal hooks. He openly discusses schemes to acquire the orphans' money and physically intimidates them when they attempt to defy their guardian's orders.

The Bald Man is a member of the theatrical troupe who wears a dark robe and has an unusually long nose. He emits high-pitched giggles and takes cruel pleasure in reminding the children of their guardian's dangerous temper and his willingness to cause them harm.

The wealthy parents of the three orphans die under mysterious circumstances in a fire that destroys their mansion. Before their untimely demise, they provided their children with a loving home, an enormous library, and the independence to travel the city on their own.

Albert Poe is one of the young sons of the estate executor. Like his brother, he is unwelcoming to the grieving orphans when they must stay at his family's home before moving to their permanent guardian.

Edgar Poe is the young son of the bank executor who manages the orphans' estate. He openly complains when the children are forced to temporarily share his crowded bedroom and is generally unpleasant to be around.