This article analyzes the conversion of peasant cultures into patrimony and "heritage" in early twentieth century France. It recounts more particularly how a seeming retreat from the wearing of traditional regional costume by the population of France's westernmost region of Brittany prompted new initiatives by regionalist and tourist advocates to safeguard it. In seeking to make Breton costume a part of a preserved and consumable cultural inheritance, the article shows, these largely bourgeois actors asserted a more decisive stewardship over the value and historical evolution of Breton culture. Yet in endeavoring to preserve and revalue an ostensibly popular cultural expression like Breton costume, this campaign introduced new forms of mediation and stirred vexing questions of cultural identity and authenticity. The most striking evidence of this shift was the genesis of new Breton cultural festivals, at which costume came to be mediated through gestures of display, promotion and performance. The article's interdisciplinary reading of these "new-traditional" events suggests that they ultimately made costume a more fluid medium of exchange—one through which Bretons and non-Bretons alike could symbolically enact their conflicted experiences of cultural continuity and change.