En this article aims at understanding the challenges of tackling complex policy problems in multilevel governance. In order to better grasp the multilevel regulation of complex policy problems, it is needed to understand how uncertainty and scientific expertise are dealt with. We investigate this via the regulation of pandemics by the eu and the who, with the h1n1 pandemic of 2009 as critical case. The analysis of the multilevel practice reveals that the attitude toward uncertainty fundamentally differed between the global (who) and the european level. At the global level a classic speaking truth to power approach involved the denial of uncertainty, while at the eu level the assigned role of providing scientific expertise was interpreted as a necessity to openly communicate about uncertainty. While the global approach was heavily criticized, the uncertainty communication at the european level was much appreciated.