The central theme of Tartuffe revolves around the stark contrast between religious hypocrisy and true Christian virtue. Tartuffe is a hypocrite because he portrays himself as deeply religious and pious while secretly engaging in immoral and criminal behavior. Throughout the play, various characters discern Tartuffe's deceit and realize he does not live according to the principles he claims to uphold. For example, Tartuffe instructs his servant to tell anyone who asks that he is busy performing charitable acts for the poor and needy, when in truth, he is trying to seduce his friend's wife. Tartuffe also maintains a façade of religious devotion by assuming a position of moral authority and dictating the conduct of everyone in the household.

Contrasting Tartuffe's deceitful actions, Molière introduces Cléante as a symbol of genuine Christian virtue. Throughout the play, Cléante articulates the distinction between true virtue and religious hypocrisy. He highlights to Orgon that truly virtuous individuals often do not feel the need to publicly display their devoutness. Cléante notes that "The truly pious people...are not the ones who make the biggest show." He further elaborates that "True piety's not hard to recognize," describing genuinely moral individuals who, instead of flaunting their religious devotion, "practice what they preach," show kindness, wish well for others, and strive to lead a virtuous life. Cléante remarks that he does not feel compelled to display his religious devotion to others because, "Heaven sees my heart."

In the play's concluding moments, Cléante once again demonstrates his deep commitment to Christian morality, particularly the value of forgiveness. When Orgon learns that Tartuffe has been arrested for numerous crimes, he begins to wish for Tartuffe to suffer for his betrayal. However, Cléante interrupts Orgon, advising him not to seek revenge but to hope that Tartuffe repents for his sins and receives a lighter sentence from the King. Cléante thereby underscores the play's message about the difference between leading a truly virtuous life and being a religious hypocrite who fails to practice what he preaches.

The theme of valuing moderation and reason over excess and obsession is a prominent motif throughout Tartuffe. The character of Tartuffe represents the dangers of excess, depicted as a glutton who indulges in food and drink at others' expense. Conversely, Orgon demonstrates excess through his obsession. His infatuation with Tartuffe clouds his judgment, almost leading to the downfall of his family. Even after realizing Tartuffe's deceit and hypocrisy, Orgon's reaction is extreme; he decides never to trust anyone again and condemns all who claim virtue. Cléante serves as the voice of reason, encouraging Orgon to choose moderation over extremes. He tells Orgon, ‘‘You never are content with moderation...you fly back and forth between extremes.'' Cléante advises that the lesson from the Tartuffe ordeal is not to distrust all seemingly good people but to avoid extreme behaviors and judgments, and to act with more deliberation. In addressing religious hypocrisy, Cléante conveys a central message of the play: moderation and reason in all aspects of life are preferable to any form of extremism or obsession.

The central theme in Tartuffe revolves around loyalty and devotion contrasted with disloyalty and betrayal. Tartuffe repeatedly betrays Orgon's trust and friendship. Orgon generously offers Tartuffe his friendship, home, food, confidence, fortune, and even his daughter, but Tartuffe takes advantage of Orgon for his own material and social gain. Tartuffe misuses Orgon’s generosity and loyalty by attempting to seduce Orgon's wife, seize his property, and have him imprisoned.

Under Tartuffe’s influence, Orgon temporarily betrays his own family by canceling Mariane and Valère’s engagement, which he had previously approved, to arrange Mariane's marriage to Tartuffe instead. In contrast, Valère exemplifies loyalty, devotion, and friendship. He demonstrates his commitment and loyalty to Orgon by risking his own safety to save Orgon from arrest. Valère arrives at Orgon's home with a carriage, urging him to flee immediately to avoid capture. He also provides Orgon with a significant sum of money for his escape and promises to accompany him on the journey, risking his own arrest for aiding Orgon's escape.

In the closing lines of the play, Orgon acknowledges Valère’s ‘‘deep devotion’’ and plans his marriage to Mariane as a reward. The theme of loyalty is further explored through Orgon’s allegiance to the King. At the play's end, the King pardons Orgon for hiding a strongbox of documents because Orgon had bravely fought on the King's side during the civil wars in France (known as the Fronde). Thus, while Tartuffe faces punishment for his betrayal, both Orgon and Valère are rewarded for their loyalty and devotion.