What are the conditions under which transnational collective action is initiated and sustained? This article presents a case study of General Motors Europe, where labor leaders have mobilized the workforce and bargained with management at the transnational level repeatedly over more than a decade as a response to management whipsawing and threats of plant closures. In contrast to structuralist interest-based theories of union behavior, we identify a process of “identity work” that was necessary to sustain transnational worker cooperation.