The national Nordic population and healthcare registers are regarded high-quality data sources for pharmacoepidemiology. Together, the different registers provide comprehensive nationwide information on drug prescriptions, healthcare contacts, and mortality in each of the Nordic countries. Through register linkage, each individual can be longitudinally followed for exposure status and health outcomes, to investigate treatment effects in nationwide pharmacoepidemiologic studies. Accordingly, the Nordic healthcare registers have provided the setting for a large number of high-profile pharmacoepidemiologic studies. However, the Nordic countries are small, and the setting of a single country may not always provide a sufficient sample size, in particular when the aim is to study orphan diseases, rare outcomes, or when studying recently introduced drugs with still limited use. A sparsely used opportunity is multi-national Nordic pharmacoepidemiologic studies, combining register data from different countries. The Nordic countries have similar healthcare systems with similar universal and comprehensive access to primary, secondary, and specialist healthcare services. Correspondingly, the national healthcare registers are similar both in structure and content. The combination of Nordic register data represents an attractive approach to provide large, representative studies based on high-quality data with sufficient sample sizes. Given the similarities in population and health care systems, pooled analysis of different countries may represent an effective and viable analytic approach. Methodological challenges include the need to take into account national differences in practice of care, e.g., diagnostic coding, referral practices, and treatment guidelines. The participation of collaborators with knowledge of health care systems and clinical practice in each country is accordingly vital. Since no common Nordic platform for research data exists, data permission and access may require substantial effort and lead-times. Despite these challenges, multi-national Nordic pharmacoepidemiologic studies can provide an attractive approach to obtain high-quality, high-precision research evidence and to fully utilize the potential of the Nordic healthcare registers.