Scholarship on transitional justice, transnational social movements, and transnational diaspora mobilization has offered little understanding about how memorialization initiatives with substantial diaspora involvement emerge transnational and are embedded and sustained in different contexts. We argue that diasporas play a galvanizing role in transnational interest‐based and symbolic politics, expanding claim‐making from the local to national, supranational, and global levels of engagement. Using initiatives to memorialize atrocities committed at the former Omarska concentration camp in Bosnia and Herzegovina, we identify a four‐stage mobilization process. First, initiatives emerged and diffused across transnational networks after a local political opportunity opened in the homeland. Second, attempts at coordination of activities took place transnational through an NGO. Third, initiatives were contextualized on the nation‐state level in different host‐states, depending on the political opportunities and constraints available there. Fourth, memorialization claims were eventually shifted from the national to the supranational and global levels. The article concludes by demonstrating the potential to apply the analysis to similar global movements in which diasporas are directly involved.