Interpretation is ubiquitous in everyday life. We constantly interpret a variety of objects. Interpretation is central to the practice of international law, too. Arguing about international law’s content is the everyday business of international lawyers, and this often includes arguing about the existence and content of norms of customary international law (CIL). Although a number of scholars recognise that CIL can be interpreted, disagreements remain as to the precise methods and extent of CIL interpretation. Such disagreements are born of a common concern to secure competently made, coherent and accurate interpretations of CIL, given the latter’s non-textual nature. This chapter aims to explore in a preliminary manner two related questions regarding CIL interpretation: (1) Is it necessary, or even possible, to strive towards coherence in the interpretation of CIL? (2) Are there any possible indicators of (in-)coherence in that respect? Providing answers to these questions depends on how one understands coherence in the first place, including its relation to legal reasoning. A substantial part of the chapter will therefore deal with that as well.