In the sixteenth and seventeenth centuries people perceived themselves as members of particular ethnic groups and considered dress to be an important marker of, alternatively, similarity or otherness. Whereas the construction of self and other in literary texts and costume books has been widely discussed, relatively little is known about the relevance of “national” dress in social practice. Against this backdrop, this article discusses the extent to which people in early modern Spain and Spanish America were able to recognize foreigners and ethnoreligious others by the way they dressed. Focusing on two groups, moriscos (Muslims converted to Christianity) within the Spanish realms and foreign Protestants, it demonstrates how a person’s outward appearance could reveal, but also conceal, his or her origin. Dress served as an important marker of ethnic and religious difference, but it always remained an ambiguous signifier.