Hans is a twenty-three-year-old engineering student from a solid bourgeois family in northern Germany. Orphaned at a young age, he possesses a cheerful but generally unexceptional demeanor, viewing life through an agreeable but prosaic lens. Intending only a brief three-week holiday at the International Sanatorium Berghof, he quickly falls under the spell of the mountain's unique atmosphere and its peculiar sense of time. His conventional mindset faces constant challenges from the eccentric residents and the competing philosophies swirling around him.

Joachim is an aspiring military officer whose career is indefinitely paused by a tuberculosis diagnosis. He treats his stay at the sanatorium like a duty, adhering strictly to the prescribed rest cures and medical routines in hopes of returning to the flatlands to serve in the military. Unlike many residents who succumb to the lethargic, decadent lifestyle of the mountain, Joachim fiercely guards his discipline and physical posture.

Clavdia is a married Russian woman who spends extended periods away from her husband to convalesce at the sanatorium. She carries herself with a distinct lack of bourgeois discipline, slouching at the table and rolling her own cigarettes. Her independent, slightly careless attitude both shocks and deeply attracts Hans, presenting him with a model of freedom entirely foreign to his strict upbringing. She considers conventional morality both restrictive and amusing.

Settembrini is an Italian humanist, writer, and staunch defender of Enlightenment values. Dressed in worn but elegant clothing, he views the sanatorium as a swamp of disease and moral decay, constantly warning Hans against falling into its lethargic traps. He values reason, progress, and democratic ideals above all else, positioning himself as a rational counterweight to the mountain's romantic obsession with illness and death.

Naphta is a brilliant, caustic scholar and Jesuit who acts as the ideological antithesis to Settembrini's sunny rationalism. He lives in a richly appointed room that reflects his complex, contradictory belief system, which blends religious orthodoxy with radical, almost terrifying visions of social upheaval. He argues vehemently that human beings require absolute authority and struggle rather than peaceful, democratic progress.

Peeperkorn is a wealthy, sixty-year-old Dutch colonialist with an overwhelming, almost elemental personality. He communicates mostly in passionate, fragmented sentences that signify intense feeling rather than logical thought. His enormous capacity for food, alcohol, and dominant social energy effectively silences the intellectual squabbles of the other residents, drawing everyone into his chaotic orbit.

Behrens is the head physician of the International Sanatorium Berghof. Following the death of his wife at the facility years ago, he slipped into a strange melancholy and never left the mountain. He commands absolute authority over the patients' schedules, diagnoses, and lives, speaking with an eccentric, breezy jargon that turns severe medical conditions into casual conversation.

Dr. Krokowski is the assistant director of the sanatorium. He conducts analytical sessions and leads strange, pseudoscientific activities like seances, blurring the line between physical medicine and spiritualism. He acts as a secondary authority figure in the residents' medical routines.

Frau Stöhr is a resident at the sanatorium known for her lack of education and tendency to butcher language. She continually misuses words and expressions, providing a source of both amusement and intense irritation for Hans and Joachim. She represents the unrefined, gossipy element of the bourgeois patients.

Marusya is a young Russian resident at the sanatorium. She belongs to the more raucous crowd and frequently wears a subtle, distracting scent. Her presence presents a constant temptation to Joachim, testing his resolve to remain emotionally detached from the sick and decadent population.

Pribislav Hippe is a schoolmate from Hans's childhood. Although they rarely spoke, Hans maintained a quiet, intense admiration for him. The memory of borrowing a pencil from Hippe returns vividly to Hans during his stay at the sanatorium, forming a psychological link to his current fascinations.

Herr Ferge is a good-natured but deeply traumatized resident of the sanatorium. He frequently recounts the horrific, almost indescribable sensation of surviving "pleural shock" during a surgery, describing it as an intense, inhuman tickling. He becomes a regular companion to Hans after Joachim's departure.

Ferdinand Wehsal is a depressed, self-pitying resident who shares Hans's infatuation with Clavdia Chauchat. Lacking Hans's reserved nature, Wehsal complains openly about his broken heart and the agonizing power that others hold over him, displaying an unappealing subservience to his own desires.

Consul James Tienappel is Hans's wealthy great-uncle and subsequent guardian. He advises Hans to pursue a practical career in naval engineering since the boy's inheritance is relatively small. Later, he briefly visits the sanatorium with the intent to bring Hans home, but the strange atmosphere quickly unnerves him.

Senator Hans Lorenz Castorp is Hans's grandfather, who takes the boy in after his parents die. He leaves a profound impression on young Hans through his dignified bearing and his connection to the family's deep ancestral past. His eventual death, and the pleasing way his body is arranged in the casket, shapes Hans's early comfort with mortality.