Some philosophers question whether higher-order evidence can support the radical skeptical conclusions that others take it to generate. Since disagreement is usually classified as being a type of higher-order evidence, these worries have in turn also been taken to cast doubts on skeptical arguments that appeal to disagreement. This chapter explores the idea that disagreement can make a belief unjustified by serving as an "undercutting defeater"; i.e., as a consideration which severs the link between the grounds we have for the belief and its truth. It is shown that this idea allows advocates of skeptical arguments from disagreement to respond to the worries about the significance of higher-order evidence.