What motivates individuals to participate in contentious, political forms of collective action? In this article, I consider the possibility that the promise of social esteem from an ingroup can act as a powerful selective incentive for individuals to participate in contentious politics. I conducted a field experiment—the first to my knowledge to take place in the context of a political march, rally, or social‐identity event—to isolate this esteem mechanism from others. Using measures of intent to attend, actual attendance, and reported attendance at a gay and lesbian pride event in New Jersey, I find evidence that the promise of social esteem boosts all three measures of participation. The article offers new theoretical and practical implications for the study of participation in nonvoting forms of collective action.