This study investigates how diverse communities across Central Eurasia crafted a particular garment type, the kaftan, into a cosmopolitan fashion in the second half of the first millennium CE. Previous scholarship has treated the kaftan as a nomadic riding ensemble adopted by settled populations for practical reasons. However, I show that in the fifth century CE, communities across Central Eurasia began to consistently construct a novel garment type according to four hallmark design features: sleeves, a fitted bodice, attached skirting, and overlapping front panels that can form lapels. This flexible but distinctive combination of features encouraged communities to modify, customize, and adorn other aspects of the garment (for example, the fabric pairing and hem length) while maintaining its recognizability. Furthermore, these personalizations did not inhibit the hallmark convertible lapel, which allowed wearers to style and re-style their garment in numerous ways instantaneously. Although the communities that adopted the kaftan were exceptionally diverse – ranging from rigidly hierarchical empires to more socially-mobile city-states, and relatively democratic nomadic polities– all of them placed the kaftan at the center of their sartorial systems. As a result, regional systems began to overlap, some mildly brushing edges and others layering over one another. As an internationally recognized fashion, the kaftan became a critical tool for cross-cultural communication. My analyses of surviving textiles, representations in wall painting and rock relief, and textual sources reveal how communities utilized the kaftan for communication. The three primary case studies are the banquet in Sogdiana (Tajikistan and Uzbekistan), the hunt in Sasanian Iran, and the funeral in Alania (Russian Northern Caucasus). Each community's approach to making and wearing a kaftan illuminates how they responded to an increasingly cosmopolitan and polycentric political landscape of first millennium Central Eurasia. Some communities, such as the Sogdians, fully embraced the kaftan's mutable design, and used it to establish subtle social distinctions in the context of transcontinental economic ventures. Some approached it more cautiously, concealing luxurious details to allow surprise transformations during difficult negotiations: for example, the Alans, who steered trade and traffic through their territory. Still others pushed against the kaftan's advancement of social fluidity. The ruling Sasanian elite manipulated the kaftan by hindering its dialogic dimension which might undermine the empire's rigid socio-political structure. Whether it produced conviviality, competition, or conflict, the kaftan delivered a cosmopolitan fashion for a cosmopolitan milieu. The kaftan equipped Central Eurasian denizens for a multitude of social, economic, and political endeavors, and allowed them to step in and out of sartorial systems for communicating on the local, regional, and international scale.