In theory, lower-level governments (provinces, regional governments, or member states) operating in multilevel systems within and beyond the nation-state can choose from a wide repertoire of modes of policy coordination to solve collective problems non-hierarchically. These modes range from unilateral policy emulation over informal intergovernmental agreements to binding interstate law. The modes that governments are willing and capable to use, however, vary considerably across multilevel systems which affects governments’ collective problem-solving capacity. This paper argues that the nature of executive–legislative relations in lower-level governments is crucial to account for this variation. The presence (or absence) of power sharing shapes the willingness of lower-level governments to enter agreements that greatly constrain individual government autonomy. Power-concentrating governments, as opposed to power-sharing ones, tend to avoid such agreements. The type of power sharing affects the capacity to enter agreements that require legislative approval. Compulsory power-sharing governments, as opposed to voluntary power-sharing governments, should find it difficult to enter such agreements, since this type of power sharing invites inter-branch divides. To substantiate these arguments, we apply them to Canada, Switzerland, the United States, and the European Union.