Support for nationalism among minorities in multiethnic countries has received a great deal of scholarly attention in recent years. Few of these studies, however, have delved into the social bases of support for nationalism within a particular ethnic group. Scholars who study nationalism usually assume that support for nationalism among the members of an ethnic group is either randomly distributed or identical for all members of the group. Both assumptions are implausible. This article seeks to show that support for nationalism among members of an ethnic group is neither constant nor random. Furthermore, it argues that the extent to which members of social subgroups within the ethnic group come to support nationalism is predictable and is based on a particular sequence of mobilization. This sequence depends on the extent to which members of each subgroup possess a sense of common collective identity and on the strength of their social ties with those who are at the forefront of the mobilization effort. Both of these factors in turn depend largely on the extent to which state institutions promote ethnic identification among the minority population and create links that increase the density of intragroup social ties. Ethnic institutions are thus the key factor in explaining the sequence by which social groups within an ethnic minority population come to support nationalism.