The Underground Man is a 40-year-old retired, low-level government bureaucrat living in an impoverished corner of Saint Petersburg. Deeply intelligent but intensely antisocial, he spends his time reading and agonizing over his perceived slights. He embraces a philosophy of scientific determinism and believes highly conscious people are doomed to inaction and self-loathing. He deliberately sabotages his own life and relationships out of spite, constantly overthinking every social interaction until he acts out in humiliating ways.

Liza is a 20-year-old woman originally from Riga who recently arrived in Saint Petersburg. Sold into sex trafficking by her family, she is deeply indebted to the owner of the "brothel" where she resides. She is timid and initially resigned to her situation, but she possesses a core desire for genuine connection and respect. Her innocence and capacity for compassion stand in direct opposition to the Underground Man's cynical worldview.

Simonov is a former schoolmate of the Underground Man who lives in Saint Petersburg. He maintains a polite but strained distance from his old acquaintance, finding his presence awkward and uncomfortable. He acts as a reluctant host and social connection, occasionally lending the Underground Man money despite recognizing his friend's toxic behavior.

Zverkov is an athletic, socially successful military officer who is preparing to transfer to a distant location. Even during his school days, he was popular and well-connected, which made him the primary target of the Underground Man's intense hostility. He possesses a confident, breezy demeanor and enjoys bragging about his romantic exploits, completely dismissing the Underground Man's attempts to insult him.

Anton Antonitch Syetotchkin is the Underground Man's older government colleague and former supervisor. He lives a modest, conventional life with his daughters and aunt. He represents the predictable society the Underground Man critiques, yet he serves as a reliable source of loans and temporary social interaction when the Underground Man's isolation becomes unbearable.

Apollon is the Underground Man's elderly, dignified servant. He acts with a haughtiness that infuriates his employer. The two exist in a constant state of mutual resentment and petty warfare, with the Underground Man frequently attempting to assert dominance over Apollon by withholding his monthly wages.

Ferfitchkin is another of the Underground Man's former schoolmates living in Saint Petersburg. He is openly antagonistic toward the Underground Man and protests his inclusion in Zverkov's dinner party. When the Underground Man gets drunk and challenges him to a duel, Ferfitchkin simply laughs at the absurdity of the threat.

Trudolyubov is a former schoolmate who joins Simonov and Ferfitchkin in organizing Zverkov's going-away party. Like the others, he is annoyed by the Underground Man's sudden appearance and attempts to exclude him from their social gathering. He joins the rest of the group in casually dismissing the Underground Man's erratic outbursts.

The Officer is an unnamed, physically imposing military man who unknowingly insults the Underground Man at a tavern by moving him aside like an object. Tall and confident, he represents the active, unthinking men the Underground Man envies and despises. He remains completely oblivious to the years-long, obsessive revenge plot the Underground Man constructs against him.

The Medical Student is a young man from Riga who knew Liza during her childhood. After reconnecting with her at a dance in Saint Petersburg, he writes her a sincere declaration of love, completely unaware that she has been forced into sex work.