Ostracism, that is, being excluded and ignored, is a common phenomenon in societies. Ostracism threatens individuals’ fundamental needs, causes pain and can result in devastating consequences such as depression or suicide. Most research on ostracism to the present date has focused on the consequences of ostracism, thereby relying mainly on laboratory studies. In contrast, the present project aims to identify and further investigate the antecedents of ostracism, that is, risk and protective factors that increase as well as decrease the likelihood for a person to become a target of ostracism. Methodologically, the proposed project goes strongly beyond prior research by utilizing a combination of panel data analysis and experimental methodology, which contribute to both a high internal as well as ecological validity. The project follows a two-step process: In the first step, possible antecedents of ostracism will be identified via cross-sectional as well as longitudinal analysis of a 2500 person sample from the SOEP-IS, a representative German longitudinal data panel. This analysis is possible because in 2014, we successfully applied for the inclusion of ostracism items into the SOEP-IS. In a second step, the mechanisms and effects of these antecedents will be further investigated in experimental studies, providing both insights about individual’s perception of stereotypical antecedents as well as individuals’ readiness to actually ostracize targets who are characterized by these antecedents (or a lack thereof). In sum, the suggested project is to provide valuable insights regarding risk and protective factors of ostracism, which has both theoretical value for research about ostracism as well as practical implications for the development of prevention programs.