The Kim family—father Ki-taek, mother Chung-sook, daughter Ki-jung, and son Ki-woo—live in a small semi-basement apartment (banjiha), have low-paying temporary jobs folding pizza boxes, and struggle to make ends meet. University student Min-hyuk, a friend of Ki-woo’s, gives the family a scholar’s rock meant to promise wealth. Leaving to study abroad and knowing his friend needs the income, he suggests that Ki-woo pose as a university student to take over his job as an English tutor for the daughter of the wealthy Park family, Da-hye. Ki-woo, presenting himself as a Yonsei University student, is subsequently hired by the Parks.
The Kim family schemes to get each member of the family a job by posing as unrelated and highly qualified workers to become servants of the Parks. Ki-jung poses as “Jessica” and, using Ki-Woo as a reference, becomes an art therapist to the Parks’ young son, Da-song. Ki-jung frames Yoon, Mr Park’s chauffeur, for having sex in the car, then recommends Ki-taek to replace him. Finally, Chung-sook takes over as the Parks’ housekeeper after the Kims exploit the peach allergy of the long-time housekeeper, Moon-gwang, to convince Mrs Park that she has tuberculosis. Ki-woo begins a secret romantic relationship with Da-hye.
When the Parks leave on a camping trip, the Kims revel in the luxuries of the residence before Moon-gwang abruptly appears at the door, telling Chung-sook she left something in the basement. She enters a hidden entrance to an underground bunker created by the architect and previous homeowner, where Moon-gwang’s husband, Geun-sae, has been secretly living for over four years, hiding from loan sharks. Chung-sook refuses Moon-gwang’s pleas to help Geun-sae remain in the bunker, but the eavesdropping Kims accidentally reveal their true identities. Moon-gwang films them on her phone and threatens to expose their ruse to the Parks.