Madame Pernelle is visiting her son Orgon’s house and uses the opportunity to criticize all the members of the household and to praise their boarder, Tartuffe, because he is a man of such holiness and zeal. The others object to Tartuffe, maintaining that he is false and hypocritical, but Madame Pernelle will not entertain such thoughts. Instead, as she leaves, she admonishes everyone to follow Tartuffe’s precepts.
After Madame Pernelle leaves, Cléante, who is Orgon’s brother-in-law, and Dorine, Orgon’s daughter’s maid, discuss the situation and their boarder and agree that Tartuffe has beguiled not only Madame Pernelle, but Orgon as well. Orgon’s son, Damis, adds to the situation by wondering out loud if his father, after being influenced by Tartuffe, will still allow his daughter, Mariane, to marry her love, Valère. Damis is also concerned because he wants to marry Valère’s sister; thus he asks Cléante to question Orgon about his earlier promise to allow the marriage to take place.
Orgon arrives and seems much more concerned about the welfare of Tartuffe than anything else around him, including his wife’s illness. Cléante tries to discuss Tartuffe with Orgon, but fails and discovers that Orgon is only interested in singing Tartuffe’s praises. When he questions Orgon about the intended wedding, he dodges the issues and refuses to give a direct answer; however, when his daughter arrives, Orgon tells her that he wants to ally Tartuffe with his house and that this can best be done by Mariane’s marrying Tartuffe. Mariane is so shocked that she cannot believe her ears.
After Orgon departs, Dorine, the maid, reprimands Mariane for not having refused to marry Tartuffe. Mariane’s beloved, Valère, arrives and accuses her of consenting to the marriage. Dorine listens to them argue and then, after they are reconciled, promises to help them expose Tartuffe’s hypocrisy.
Damis, incensed about Tartuffe, is also determined to reveal Tartuffe’s hypocrisy, and, as he hears Tartuffe’s approach, he hides in the closest. Elmire, Orgon’s wife, arrives, and Tartuffe, thinking they are alone, makes some professions of love to her and suggests that they become lovers. Having heard Tartuffe’s plans, Damis reveals himself and threatens to expose Tartuffe. When Orgon arrives, Damis tries to inform his father about Tartuffe’s proposition, but Orgon is so blind that he thinks his own son is evil in trying to defame Tartuffe’s good name—and he immediately disinherits his son. As Orgon and Tartuffe leave, Orgon reveals his plans to make Tartuffe his sole heir and also his son-in-law.
Cléante later confronts Tartuffe and tries to reason with him, but Tartuffe will only respond in religious clichés, and, as soon as the opportunity presents itself, he hastily excuses himself from the room. Orgon and Elmire arrive, and when she hears Orgon’s plans, she extracts a promise from him to hide in some concealed place and observe Tartuffe’s actions. Orgon consents, and Elmire sends for Tartuffe. When he arrives, he is accosted by Elmire, and soon he begins to make not only declarations of love to her but also derogatory comments about Orgon.
Finally convinced of Tartuffe’s hypocrisy, Orgon emerges and orders him from the household. Tartuffe then reveals that legally he is now the owner of the house, since Orgon has signed over all his property. Alone with his wife, Orgon reveals that he is frightened because, earlier, he had entrusted some secret documents to Tartuffe’s care–documents which could ruin Orgon’s trusted position in the court.
When Orgon’s mother arrives, he cannot convince her that Tartuffe is a hypocrite; it is only when news arrives that Tartuffe is having the entire family evicted that Madame Pernelle is convinced. Tartuffe brings with him officers of the court, but, as the family is about to be evicted, an officer reveals that the king has seen through the hypocrisy of Tartuffe and has ordered him to be imprisoned for this and for other crimes. The king has also restored to Orgon all his rightful property.
