The research objective is to analyse the consequences that recent crises have had for multilateral organizations, to what extent they fostered a transformation of response mechanisms and whether this transformation has contributed to strengthening the institution and improving its response to new crises. We analyse and compare the role of two specific International Organizations (IOs), the World Health Organization and the International Organization of Migration, in recent major transnational crises: the COVID-19 pandemic and the migration crisis caused by Russian aggression against Ukraine.Two complementary strands of the scientific literature are taken into account: Studies analysing the functioning and performance of IOs and the literature on crisis management. In each case study, we describe the IOs’ institutional designs and the characteristics of the policy regimes in which the IOs operate. Then we assess the response given to the crises, distinguishing between planned measures designed to provide an immediate response and resilience measures for future crises. We end with a comparative assessment of the performance of these two IOs in the face of these crises and their capacity to learn lessons from them to deal with future crises.