In Aristotle's definition of the tragic hero, such a person must be highborn, have a fatal flaw, and engage the "pity," or sympathy, of audience members, who side with her and feel sorrow in her fall.

The duchess can be called a tragic hero. As a duchess, she is highborn. Her fatal flaw is not quite a flaw like the pride or hubris that takes down Oedipus and Creon, but it is a flaw in the context of the corrupt world she lives in: the duchess is too trusting and good. She should, for example, know better than to be deceived by Bosola's feigned loyalty to Antonio, but she does not. She should try to destroy her brothers, but she does not.

Her flaw is paradoxical. It raises audience sympathy and leads to her downfall, which helps make the duchess a tragic hero; but it is also a flaw that might be seen in a positive light, because it affirms her humanity in the face of the inhumanity of her brothers.

The duchess's trusting and good nature may initially appear to be a virtue, but in the context of her story, it is a flaw. Standing up to enemies, especially tyrannical rulers, is rarely seen as evil: for example, readers don't view Malcolm in Macbeth as evil for bringing an army to Scotland to fight the monster Macbeth. But the duchess's flaw is not her kindness or virtue, but the stereotypical female flaw of being too kind. In her case, her kindness proves to be an impediment.

While on the whole, the duchess is a tragic hero whose flaw undoes her, she also does not suffer the wholly tragic fate of losing everything: in a way, she has the ultimate triumph, because her son survives to inherit her kingdom while her brothers die because of their own misdeeds. Nevertheless, her fate is tragic.