This article asks how international secretariats can sometimes expand their authority in areas that relate neither to their mandate, nor to their sphere of expert authority. Existing explanations of mission creep assume that IOs act autonomously and expand in those areas that connect with their mandates, sense of organizational mission, and sphere of expert authority. The claim here is that entrepreneurial bureaucrats can succeed—in the absence of policy deadlock among states—in creating creep in unexpected issue domains through the mobilization of external expertise. The article examines this dynamic in the domain of bioethical standards. It shows that UNESCO acted as a first mover in the field, despite having no relevant expertise, and despite bioethics being more closely connected to the mandate of other organizations. Entrepreneurial bureaucrats within UNESCO were able to create creep in bioethics by mobilizing external experts in the field and capturing their skills. Working with external experts endowed their organization with the capacity to act, gave epistemic authority to their actions, and prevented the politicization of debates in a potentially controversial issue domain. In pointing to the strategic uses of expertise, the article challenges the commonly held view that expert knowledge acts as a means of solving problems and rationalizing global governance.