This paper discusses how the political and commercial activities of the Dutch East India Company affected the territorial powers of Lonckjouw in southern Formosa. The contemporary Dutch portrayed the Lonckjouw people as the most stratified society in Formosa. Their leaders ruled over more than 16 villages and acted as lord of all his subjects. This paper explores how the development of the Dutch commercial and political interests in southern Formosa simultaneously enhanced and impeded the territorial expansion and political consolidation of the Lonckjouw people. The leadership of the Lonckjouw people once declined, and even tentatively split, after the Dutch moved their alliance to the Pimaba to the north of Lonckjouw. By analyzing the contemporary political geography and interactions between the Lonckjouw people and the Dutch, the paper shows how the Lonckjouw leaders responded to the Dutch in an effort to maintain their dominance, while facing the Dutch presence from southwestern Formosa.