There's a storm brewing at Orgon's house. According to his mother, Madame Pernelle, Orgon's family has become decadent and depraved. They're unable to see the greatness of Tartuffe, a beggar and holy man Orgon recently took in. According to the rest of Orgon's family, Orgon has been "taken in." They think Tartuffe is a hypocritical, self-righteous con artist. When Orgon returns from the country, we find that he's become obsessed with Tartuffe; he would rather hear about him than about his sick wife. Orgon is offended when his brother-in-law, Cléante, tells him he's been acting like an idiot. When Orgon attempts to explain why Tartuffe is such a great and admirable man, Cléante sees right through his brother-in-law's unsound reasoning. Cléante asks Orgon about the rumored postponement of Mariane's (Orgon's daughter) wedding. Orgon confirms that it has indeed been postponed, but he will say nothing further. Cléante is rightfully concerned.
Orgon calls Mariane in for a chat. He wants to know how she feels about Tartuffe. When she acts surprised, he tells her how she's supposed to feel: she respects him, is fond of him, and will marry him. Mariane is speechless, but luckily Dorine, a saucy servant, isn't. She comes in and asks Orgon if Mariane is really going to marry Tartuffe. When her boss confirms this, she makes fun of him, calling the idea ridiculous. Dorine proceeds to annoy Orgon, preventing him from talking further with Mariane.
Once Orgon leaves, an irritated Dorine tells Mariane that she can't believe how weak she acts in front of her father. Although she is hard on Mariane, Dorine eventually relents and agrees to help the girl. Valère, Mariane's fiancé, enters. He's heard the bad news about their wedding plans. Soon enough he and Mariane are arguing over nothing in particular. Dorine gets them to kiss and make up. The clever servant instructs Mariane to stall the wedding to Tartuffe and tells Valère to spread word of Orgon's foolishness around town.
When Damis, Orgon's son, hears about his father's plan to marry Mariane to Tartuffe, he flips out and tells Dorine that he's going to give Tartuffe a knuckle sandwich. Dorine has a better idea: she's arranged for a meeting between Tartuffe and Elmire, Orgon's wife. Damis insists on watching, and spies on the conversation while hiding in a closet. During the meeting, Tartuffe makes a rather awkward attempt to seduce Elmire. When he fails, Elmire strikes a deal with him. If he refuses to marry Mariane, she says, she won't tell Orgon about what just happened. While Tartuffe seems fine with this, Damis does not. He leaps from the closet and confronts Tartuffe. When he tells Orgon – who just happens to walk in – what he's just seen, Orgon doesn't believe him. As a result, Orgon disinherits Damis and gives Tartuffe the rights to his whole estate.
Cléante attempts to reason with Tartuffe and get him to give Damis a second chance, but Tartuffe refuses. All the while, things get worse: Mariane can no longer bear the stress of her impending marriage. When Orgon appears, marriage contract in hand, Mariane, Dorine, and Elmire plead with him. Though he has pangs of conscience, he stands firm. Elmire takes matters into her own hands, and promises to show him the truth about Tartuffe. She makes him hide under a table and tells Dorine to call in Tartuffe.
When Tartuffe arrives, she does her best to "seduce" him. He is skeptical of the whole situation, given the quick about-face, and demands that she give him some concrete sign of her affection. Elmire becomes increasingly antsy, and eventually asks Tartuffe to step outside the room and look to make sure her husband – Orgon – isn't around. When he does, Orgon pops out from under the table, enraged. Elmire tries to get him to hide again, in order that he might watch more and really make sure he's satisfied, but Tartuffe comes in before he can hide. When Orgon confronts Tartuffe, Tartuffe reminds him that he has the rights to Orgon's property and promises to get his revenge.
As it turns out, not only does Tartuffe have the rights to Orgon's property, he also has a number of documents that, if they were to come to the attention of the King, could get Orgon in serious trouble. Damis returns, ready to fight Tartuffe – literally – but he's interrupted by Madame Pernelle. She can't believe the rumors she's heard about Tartuffe. Orgon attempts, unsuccessfully, to convince her, and only becomes frustrated in the process. Their argument is cut short by the arrival of Monsieur Loyal, a messenger sent by Tartuffe. He serves Orgon with a notice of eviction, and let's them know that he and his family should be out of the house by the next morning. Just when things seem like they couldn't get any worse, Valère comes in and tells Orgon that he must flee the country, as Tartuffe has denounced him to the King.
Orgon is just about to leave with Valère, when Tartuffe shows up, accompanied by a police officer. He tells Orgon what he already knows and, after being insulted, tells the officer to arrest Orgon. The officer arrests Tartuffe instead, telling Orgon that the King saw through Tartuffe's scheme immediately. Turns out, Tartuffe is also a well-known criminal. Orgon is pardoned by the King, on account of his loyalty and prior aid to the Crown. Orgon begins to curse Tartuffe, but Cléante makes him stop. Instead, he tells Orgon, we should pray for his salvation. Orgon relents, and tells everyone to get ready to see the King. Once the King has been properly thanked, Orgon says that Valère and Mariane can finally be married.