We aim to develop a form of debunking argument according to which an agent’s belief is undermined if the reasons she gives in support of her belief are best explained as rationalizations. This approach is a more sophisticated form of what Shaun Nichols has called best-explanation debunking, which he contrasts with process debunking, i.e., debunking by means of showing that a belief has been generated by an epistemically defective process. In order to develop our approach, we identify an example of such a best-explanation debunking argument in Joshua Greene’s attack on deontology. After showing that this argument is not an instance of process debunking, we offer our best-explanation approach as a generalization of Greene’s argument. Finally, we defend our approach by showing that it is not susceptible to some criticisms that Nichols has leveled against a less sophisticated form of best-explanation debunking.