Why do some people participating in transnational protest events identify with their foreign counterparts while others participating in the same events do not? We find that participants in a series of May Day and climate change events are aware that the events are part of a broader struggle, and many in fact identify with their overseas counterparts. However, there are differences between demonstrations. Some are populated with people who identify transnationally, while others are comprised of participants who more closely identify with their national companions. Focusing on differences in transnational identification at the participant level, our findings can be summarized in two statements: (1) protest participation is a stronger producer of transnational identification than associational activism; (2) expressive protesters identify more transnationally than instrumentally motivated protesters.