Witness evidence plays a lead role in international arbitrations, yet the reliability of witness evidence in arbitral contexts has received little attention from legal practitioners. Hundreds of scientific studies have highlighted the fragile nature of witness memory and the ease with which memories can become unwittingly corrupted. In this article, we explain why the psychological research on witness memory is relevant to international arbitration and outline some of the key findings that have important implications for procedure and practice. Alongside the large body of science illustrating the malleability of witness memory, there exists a substantial amount of research outlining how best to preserve or maximize the quantity and quality of witness evidence. Indeed, many simple measures can be adopted by arbitrators and counsel, when eliciting and presenting witness evidence. When educated on the psychological science concerning the factors that can render even the most meticulous and honest witness prone to error, fact-finders will be in a far better position to assess witness evidence in international arbitrations.