Congo. Baptism is supposed to be a time of happiness and joy. This does not occur and the villagers become frightened of baptism because of the river and their mistrust of Nathan.

An example of verbal irony in this novel occurs when Nathan mispronounces the language of the villagers. He intends to preach that "Jesus is precious" and a treasure but actually says that "Jesus is poisonwood". This mistake shows that Nathan is unlikely to find success with his mission to save the people of the Congo.

The novel's title encapsulates a central irony of the novel: it reflects Nathan Price's mispronunciation of the native words for "Jesus is precious," such that the Congolese hear instead that "Jesus is poisonwood." Ironically, the Jesus preached to the Congolese by arrogant Western missionaries like Nathan is poison to the Congolese people, something they need to stay away from. People like Price, intending to bring salvation to the Congo, bring disaster. 

Nathan represents the way white patriarchy comes into a native culture without any attempt to respect or understand the people with whom it is interacting. Nathan believes he comes from a far superior culture and has all the answers and nothing to learn. He tries to dynamite fish out of the water, in part to impress the Congolese, who are not impressed. He pays no attention to how the Congolese plant or farm. Ironically, if he had paid more attention to his hosts' way life and treated them as equal human beings, he would have had a greater chance of succeeding as a missionary—and of successfully surviving himself. 

Another irony of the novel is that the supposedly inferior black villagers, though often damaged and crippled, are more competent and humane—more Christlike—than the Christians.

The ultimate irony in The Poisonwood Bible revolves around the death of the youngest daughter Ruth May.  The village in which the Price family lives is plagued by ants and two of the daughters run to safety.  Adah, who is handicapped, and Ruth May are left behind.  Orleanna reasons that when in trouble a mother needs to care for her children from the bottom up, so she saves Ruth May and leaves Adah behind.  Adah is then saved by a man in the village.  Later, someone plants poisonous snakes outside the Prices' home, and one bites and kills Ruth May, the daughter whom Orleanna tried to protect.  This is significant because it is at this point that Orleanna decides to take control of her family and leave the Congo.  Nathan Price has not listened to Orleanna's prior pleas to return home, and Orleanna has accepted her husband's desire to continue his mission.  Now, the death of their daughter forces Orleanna to take action.