Ethnic identification (i.e., one's self-reported ethnicity) is a social construction and therefore subject to misperceptions by others. When adolescents' self-views and others' perceptions are not aligned, adolescents may experience adjustment challenges. The present study examined mismatches between adolescents' ethnic identification (i.e., self-reported ethnicity) and meta-perceptions (i.e., what ethnicity they believed their schoolmates presumed them to be), as well as longitudinal associations between mismatches and adjustment across the high school years. Participants (Mage = 14.5; 57% girls) were an ethnically diverse sample of 1151 low-income high school students who had participated in an earlier longitudinal study during middle school. Although ethnic identification was largely consistent across the high school years, many students (46%) experienced at least occasional mismatches between their self-reported ethnic identification and meta-perceptions, with students who ever identified as multiethnic experiencing more mismatches than their monoethnic counterparts. Experiencing a mismatch was associated with more depressive symptoms, physical symptoms, and lower self-worth.