.Deep disagreements are those involving a disagreement about (relatively) fundamental epistemic principles. This paper considers the bearing of testimonial injustice, in Miranda Fricker’s sense, on the depth of disagreements, and what this can teach us about the nature and significance of deep disagreements. I start by re-evaluating T. J. Lagewaard’s recent argument that disagreements about the nature, scope, and impact of oppression will often be deepened by testimonial injustice, since the people best placed to offer relevant testimony will be subject (...) to testimonial injustice, pushing the disagreement into one about the bearing of certain epistemic sources on the original debate. I take issue with this last step, but I build on the argument to bring attention to unappreciated and worrying ways in which prejudices can make a disagreement deep in ways that can be hidden from one or more of the participants and from observers. Finally, I revisit some of the ways that deep disagreement has been thought to be problematic for the proper functioning of a democracy, and I examine whether the kinds of hidden deep disagreements I argue for in the paper make these problems any worse, concluding that they likely do. (shrink)