Background: Early awareness and alert systems have been established in many countries but evidence on their ability to accurately prioritize new medicines (for early assessment) is limited. Objective: The purpose of this study was to assess whether the Swedish Early Awareness and Alert System identified and prioritized (i.e., produced early assessment reports for) new medicines that would go on to have substantial economic impact. Methods: We adapted a study design commonly used in the assessment of diagnostic test accuracy. The prioritization made by the Swedish Early Awareness and Alert System prior to marketing authorization comprised the index test and the national drug sales data in the second year post-authorization served as the reference standard. All initial marketing authorization applications for medicinal products processed by the European Medicines Agency between 2010 and 2015 (study population) were classified using the index test and the reference standard. Results: Two hundred and fifty-three new medicinal products processed by the European Medicines Agency comprised the study population. Of these, 71 were prioritized by the Swedish Early Awareness and Alert System and 21 were classified as having substantial economic impact. The sensitivity and positive predictive value were 76.2% and 22.5%, respectively. Subgroup analyses showed that the accuracy of prioritization, in terms of sensitivity, was 100% for antineoplastic/immunomodulating agents. Conclusions: The Swedish Early Awareness and Alert System identified all new medicines that would go on to have substantial economic impact and prioritized most of these medicines. Our findings provide reassurance to decision makers who rely on the outputs of the Swedish Early Awareness and Alert System to keep informed about new medicines. Moreover, this study also provides valuable insights to stakeholders willing to establish or evaluate their own early awareness and alert activities and systems.