Ethnicity is frequently posited as an important factor in civil violence and other political contexts. Despite the attention that ethnicity receives, its effects depend on an important, but mostly ignored, assumption that ethnicity is identifiable within and across groups. There is likely considerable variation in peoples’ abilities to identify each other. Certain individuals within groups might be better at identifying others’ ethnicities; further, different types of information might aid identification better. We contend that the strength of an individual’s ethnic identity influences her ability to identify others correctly. We test this argument using an experiment in the Eastern Cape of South Africa in which individuals attempted to identify members of the major black ethnic groups. We find that the average individual struggles to identify ethnicity correctly in many conditions. Individuals with a stronger identity, however, are often better at correctly identifying the ethnicity of others relative to the average individual. When receiving contradictory information, individuals with stronger identities were sometimes deceived more easily than others. These results have implications for a diverse set of studies relying on the identifiability assumption.