The private enforcement of EU competition law depends on national remedial and procedural rules. Both EU law and national rules require a causal link to be established between a harmful event and the resultant harm. The content of this causal link is mostly a matter for national rules. The ECJ case law on the nature of said causal link therefore remains underdeveloped, even though the issue of causality is highly relevant as it concerns every private enforcement case. This article explores the implications of the EU competition law notion of “single infringement” for private enforcement in general and for the understanding of the concepts of “harmful event” and “causal link” in particular. EU-level case law is analysed to determine how the finding of a single infringement could impact private enforcement. It is argued that EU competition law likely affects the application of national causality rules by defining the relevant harmful event through the concept of “single infringement”.