Historical political entities differ in their understanding of sovereignty. This paper studies how conceptualizations of sovereignty clashed during the peace negotiations between the Spanish Monarchy and the United Provinces of the Low Countries held during the 1640s. It argues that these different understandings of sovereignty posed a significant obstacle to the signing of the peace and, once signedm remained a potential source of instability in the relationship not only between both polities but also for the internal equilibrium of the Dutch Republic.