A number of recent decisions issued by the International Centre for the Settlement of Investment Disputes (ICSID), which address jurisdictional interactions between national and international proceedings, have sparked renewed interest in the possibility of identifying jurisdictional overlaps between the two groups of judicial bodies. Arguably, these ICSID cases are indicative of a broader tendency to reassess the relationship between national and international courts, which also takes place in other areas of international law, such as human rights law, criminal law and law of the sea. The article explores whether the jurisdictional relations between national and international courts can conceivably qualify as ‘competing’ or ‘overlapping jurisdictions’ – i.e., jurisdictions that have the potential of addressing, in parallel, the same disputes (involving the same parties and the same issues), under the existing definitions of jurisdictional competition or overlap and posits that such jurisdictional relations could theoretically be conceptualized in situations where the two sets of judicial institutions operate in a non-hierarchical context. Furthermore, the article seeks to examine what jurisdiction-regulating rules and principles, if any, could be applied to such a putative set of jurisdictional relations. It suggests that given the considerable theoretical difficulties which the introduction of traditional jurisdiction-regulating rules, such as res judicata or lis alibi pendens entails, resort to more flexible legal doctrines such as judicial comity and the prohibition against abuse of right could be more useful.