Professor Otto Lidenbrock is a 50-year-old mineralogist and geologist who teaches at the Johanneum and curates a museum in Hamburg. He is a tall, thin man with an iron constitution and an intensely obsessive personality, willing to starve himself and his household when absorbed in a puzzle. His scholarly brilliance is paired with a short temper and a lack of social grace, making him a formidable but difficult man to live with.

Axel is an orphaned young man living with his uncle in Hamburg, acting as his assistant and managing a collection of mineral specimens. He has a deep love for mineralogy but lacks his uncle's fearless, obsessive nature, often prioritizing physical comfort and safety. He narrates the story and serves as the cautious counterweight to his uncle's reckless ambition, actively doubting the wisdom of their impending journey to Iceland.

Hans is a large, physically powerful Icelandic eider-duck hunter who agrees to guide Otto and Axel. He possesses a remarkably calm, silent demeanor that sharply contrasts with the professor's nervous energy. As a practical outdoorsman, he knows how to travel across the harsh local environment and provides essential survival skills for the planned expedition.

Gräuben is Otto's 17-year-old goddaughter, a serious and scientifically minded young woman living in the Hamburg household. She helps manage the professor's mineral collection and harbors a secret engagement to Axel. Despite the gender constraints of her era, she displays considerable bravery and enthusiasm for the expedition, encouraging Axel to embrace the adventure.

Martha is the housekeeper for the Lidenbrock residence in Hamburg. She manages the daily domestic routines but frequently struggles to accommodate Otto's erratic schedule and obsessive behavior, particularly when he locks down the house or refuses to allow meals.

Arne Saknussemm is a 16th-century Icelandic alchemist whose works were burned due to accusations of heresy. He leaves behind a coded message written in reverse Latin, claiming to have discovered a passage to the center of the Earth. His historical legacy drives the entire plot forward.

M. Fridrikson is a professor of natural science at the local school in Reykjavik. He acts as a hospitable local contact for the travelers, providing them with lodging, information about Icelandic history, and the crucial recommendation to hire Hans as their guide.