It is uncontroversial that we sometimes have moral obligations to voice our disagreements, when, for example, the stakes are high and a wrong course of action will be pursued. But might we sometimes also have epistemic obligations to voice disagreements? In this paper, I will argue that we sometimes do. In other words, sometimes, to be behaving as we ought, qua epistemic agents, we must not only disagree with an interlocutor who has voiced some disagreed-with content but must also testify (...) to this disagreement. This is surprising given that norms on testimony are generally taken to be permissive, and epistemic obligations are usually taken to be negative. In this paper I will discuss some occasions in which epistemic obligations to testify may arise, and I will attempt to investigate the nature of these obligations. I'll briefly discuss the relationship between epistemic and moral norms. I'll offer an account of what it takes to discharge epistemic obligations to testify. Finally, I'll look at some accounts of epistemic obligation that might explain these obligations. (shrink)