As a young man, Okonkwo becomes one of the greatest wrestlers in the clan. Okonkwo values strength and aggression, traits he believes are masculine, and his worst fear is to be thought of as feminine or weak, like his father, Unoka.
Okonkwo's wealth and status within the tribe grow, and he becomes one of the greatest men in the land, with three wives and a large stock of yams. He treats his family with a heavy hand, believing that the only emotion worth showing is anger. Okonkwo is particularly worried about his eldest son, Nwoye, in whom he sees signs of laziness reminiscent of Unoka.
One day, the clan settles an argument with a neighboring village by demanding the sacrifice of a virgin and a 15-year-old boy named Ikemefuna, who lives with Okonkwo's family for the next three years.
While living with Okonkwo's family, Ikemefuna becomes very close to Nwoye, sharing folktales and encouraging him to enjoy masculine tasks. Okonkwo approves of his influence on Nwoye and grows fond of Ikemefuna himself. Ikemefuna soon starts to call Okonkwo “father.”
After three years, when the oldest man of the tribe, Ezeudu, informs Okonkwo that Ikemefuna must be killed, he advises him not to participate in the killing, since “the boy calls you father.” Okonkwo ignores this advice, fearing that others will find him weak or effeminate, and he proceeds to strike the killing blow when they take Ikemefuna out to be killed the next day.
Soon, Ezeudu passes away, and his funeral celebration draws the entire clan. During the burial, Okonkwo's gun explodes, killing Ezeudu's 16-year-old son. Having killed a fellow clansman, Okonkwo has no choice but to flee the clan with his family. Because the crime is a “female,” or accidental, crime, they may return in seven years.
During their time in exile, Okonkwo and his family work hard to start a new farm in Okonkwo's motherland, Mbanta. His mother's kinsmen treat them kindly, but Okonkwo is extremely discouraged by the circumstances. He plans for the day he can return to his rightful place in Umuofia.
While he works in Mbanta, the white men begin to appear among neighboring clans, causing stories to spread about their power and destruction. When they finally arrive in Mbanta though, the clan is fascinated but finds their religion ridiculous. Nwoye, however, is captivated by the hymn he hears on the first day, and soon joins the Christians to get away from his father, who is outraged.
When Okonkwo finally returns to Umuofia, the white men have changed his clan as well. Mr. Brown, a white missionary who is popular for his patience and understanding approach, has built a school and hospital, and many clan members are enrolling their children in the school so that they can one day become clerks or teachers. However, soon after Okonkwo's return, Mr. Brown leaves the country due to health reasons, and Reverend Smith replaces him.
Reverend Smith is uncompromising, encouraging acts among the converted clan members that provoke the rest of the clan. When Enoch, a fanatical convert, rips the mask off of one of the clan's masked egwugwu during a ceremony. The clan retaliates by burning down the church. Reverend Smith reports this transgression, and the District Commissioner tricks the clan's leaders into meeting with him before handcuffing them. The clan leaders, including Okonkwo, suffer insults and beatings before they are released once the village pays the fine.
The morning after their release, the clan leaders speak of war before they are interrupted by the arrival of court messengers. Full of hate, Okonkwo confronts the leader, who says that the white man commands the meeting to stop. In a flash, Okonkwo strikes down the messenger with his machete. Seeing that none of his clansmen support him in his violent action, Okonkwo walks away and hangs himself.
When the District Commissioner comes to fetch Okonkwo the next day, the clansmen lead him to his hanging body instead, saying that they cannot touch it, since it's an abomination for a man to take his own life. The District Commissioner finds this custom interesting, making note of it for his book on Nigeria, which he plans to title The Pacification of the Primitive Tribes of the Lower Niger.