Based on the authors’ fieldwork, we present three key findings about the lexical prosodic system of the Kohama dialect of Yaeyama. First, we show that the Kohama dialect distinguishes between three different tone classes. Second, like many other dialects of Southern Ryukyuan, we show that the prosodic word, defined as a prosodic unit between the syllable and the minimal syntactic phrase, needs to be posited in order to achieve an adequate generalization of the pitch patterns of each tone class. Lastly, we observe that the three tone classes of Kohama regularly correspond to the tone classes reconstructed in proto-Ryukyuan.