Most research on protests has been conducted in peaceful societies, whereas we know far less about contentious collective action in postwar contexts. To fill this gap, we offer a theory that perceived ethnic grievances related to group security and group status are particularly likely to generate protest mobilization in postwar societies. To test this theory and alternative hypotheses, we investigate trends in protest behavior in postwar Kosovo using an original protest event dataset and existing survey data. We find that protest behavior in postwar Kosovo is significantly shaped by perceived ethnic grievances: the majority of protest grievances center around group security and group status concerns. Protests about economic justice or good governance demands are significantly rarer. Using data from existing surveys, we also investigate the determinants of variation in individual protest participation. Our analysis reveals that perceived ethnic discrimination is strongly associated with individual protest participation in Kosovo.