Over fifty years after its original publication, To Kill a Mockingbird still faces some challenges over its inclusion in school classrooms and libraries. The most common complaint against the book since the 1960s has been its use of the n-word, a criticism also leveled against Mark Twain's The Adventures of Huckleberry Finn.

Lee's novel also tackles mature themes and features some violent content, including Bob Ewell's attempted murder of the Finch children, the book's discussion of rape, and the references to child abuse (both physical and sexual). Parents often question if their children are too young for the book's content and believe it may be traumatizing if they are exposed to it too early, which is perhaps the most common reason any book is challenged or banned in school libraries.

In recent years, some parents have argued for the book's censorship because they believe its messages about race are outdated and no longer adequate in the modern world, or that such messages are even harmful. Atticus Finch is seen as a "white savior" figure by some, and others believe the book's depiction of racism is flawed since it comes from a white point of view. Others view the book's depiction of racism as potentially upsetting to young Black readers.