The article examines the role of precedent in investment treaty arbitration. It reviews different approaches to the role of precedent taken in arbitration literature so far. The authors submit that, while it is sure that there is no formal doctrine of precedent in the area of investment treaty arbitration, empirical research shows that arbitrators regularly refer to earlier cases. Yet, due to the fact that arbitral tribunals are not bound by earlier arbitral decisions, it may sometimes prove somewhat difficult for parties to foresee whether arbitrators will follow earlier cases in their decision-making process.