Constitutional conventions are rules of political practice accepted as binding by those concerned in the working of the constitution. This peculiar category of constitutional rules occupies an important position in the constitutional systems of many states, including the United Kingdom and the Netherlands. Whereas in the United Kingdom much scholarly attention has been paid to conventions, the study of conventions in the Netherlands is still in its infancy. One of the questions that features prominently in the academic and judicial debate in the UK is whether conventions, despite not being legal rules, can be enforced by the courts. This question has hitherto not been discussed in the Netherlands. The objective of this article is to look at the legal relevance, or irrelevance, of constitutional conventions in both jurisdictions and to find explanations for the observed differences and similarities in this regard. First, this paper analyses the legal relevance of constitutional conventions before courts in the United Kingdom and the Netherlands respectively. Second, this paper compares the two jurisdictions with regard to this matter and tries to find constitutional explanations for the observed differences and similarities. In analysing this issue, the article attempts to provide an example of how comparative legal research in the area of constitutional law can foster the development of constitutional concepts.