Kim Gi-taek (Song Kang-ho), an unemployed driver, lives with his wife Park Chung-suk (Jang Hye-jin) along with their children named Kim Gi-u (Choi Woo-shik) and Kim Gi-jeong (Park So-Dam) in a bad cellar. Their daily job is folding pizza boxes. One day, Gi-u’s friend, Min-hyuk (Park Seo-joon) visits Kim’s family. Min-hyuk plans to study abroad, thus suggesting that Gi-u take over his job as English tutor Park Da-hye (Jung Ji-so), daughter of rich family Park Dong-ik (Lee Sun-kyun) and his wife Choi Yeon-gyo (Jo Yeo-jeong) and brother of Park Da-song (Jung Hyun-joon). Gi-u is willing to accept his friend’s offer.
Yeon-gyo who knows Gi-u replaces Min-hyuk immediately accepts Gi-u gladly. Gi-u was shocked by the view of the rich family’s house which he considered stunning. Gi-u also saw a Da-song painting. When Yeon-gyo intends to find an art teacher for Da-song, Gi-u takes advantage of this opportunity by suggesting a “professional” named Jessica from the United States who turns out to be his own brother Gi-jeong. Gi-jeong manages to win Yeon-gyo’s heart for making Da-song obey Gi-jeong’s orders. Intending to get his father into the house, Gi-jeong slanders Park’s driver by putting his underwear in Park’s family-owned car. Dong-ik drives the driver away and replaces him with “Uncle Kim” who turns out to be Gi-taek, according to Gi-jeong’s advice. Gi-taek connects with his two children to make Mun-gwang (Lee Jung-eun) leave the house. The two children sprinkled peach powder on Mun-gwang, while his father took a photo in front of Mun-gwang who was waiting at the hospital. Gi-taek suggests that Dong-ik hire someone from the Care agency (a fake company of his own fiction) who turns out to be Chung-suk. Dong-ik believes in Gi-taek when he sees the Care business card which he thinks is luxurious, so Chung-suk succeeds in becoming a housemaid at the house. One day, the Park Family camped for a day and night as a present for Da-song’s birthday, so the Kim Family partyed while drinking in the house one day and night.
When at night when it was raining heavily, the excitement vanished when Mun-gwang rang the bell and asked to be allowed in because he wanted to take something in the basement. While the whole family is hiding, Chung-suk lets Mun-gwang in. In the basement, Mun-gwang opens a secret door to the bunker, where her husband Geun-se (Park Myung-hoon) has been hiding for four years to avoid loan sharks. When Chung-suk threatens to call the police, another family stumbles upon him and accidentally calls by his real name. Without thinking, Mun-gwang seized the opportunity by recording them and planned to send the recording to the Park Family. Mun-gwang and Geun-se “captured” them by treating them as if they were prisoners of the North Korean president Kim Jong-un. When Mun-gwang and Geun-are off guard, the Kim Family tries to grab Mun-gwang’s cellphone and everyone fights with each other. Kim’s family finally managed to get the cellphone and immediately deleted the recording. Due to rain, Park’s family canceled their vacation and called Chung-suk. The Kim family seizes Mun-gwang and Geun-se in the bunker and cleans the living room and then hides, while Chung-suk makes ramyeon as Yeon-gyo requests. Mun-gwang manages to free himself and runs to the living room, but Chung-suk kicks him so Mun-gwang bounces down. Chief Mun-gwang hit the wall and was seriously injured.
After several close calls, Ki-taek, Ki-jeong and Ki-woo leave the mansion undetected. The three ran back to their poor neighborhood, which had been hit by a storm. They save what they can from their home, Ki-woo carries a big “lucky stone” Min-Hyuk presents his family. The three of them, along with other displaced people, slept in the gym. Meanwhile, Moon-kwang dies of a concussion when Geun-sae cries.
The following day, Mrs. Park held a birthday party for Da-song and invited Kims to participate. During the party, Ki-woo brings a stone to the bunker, intending to kill Geun-sae. Geun-sae ambushes Ki-woo and opens his head with a stone. Armed with a knife, Geun-sae crashes into a party and stabs Ki-jeong in the chest. His appearance triggers a traumatic memory of Da-song and the boy starts having a seizure. Ki-taek rushes to stop Ki-jeong’s bleeding when Mr. Park shouts at him to throw the car key so that Mr. Park can take Da-song to the hospital. The key that was thrown was trapped under the battle of Choong-sook and Geun-sae before Choong-sook killed Geun-sae with a dead key.