Despite having no such explicit mandate, IOM is one of the largest global actors in IDP response and protection. Yet, its activities on behalf of IDPs have been remarkably under-studied. This chapter appraises IOM’s obligations under the UN Guiding Principles on Internal Displacement (GPs), and assesses the extent to which IOM applies these in its work. The chapter does so in two main ways. First, by mapping references to IDPs and the GPs in IOM’s policies, and, second, by examining how these policies are implemented in practice in two country contexts – Haiti (disaster displacement) and Iraq (conflict-induced displacement). While important to recognise the positive impacts of IOMs IDP protection efforts, this chapter identifies and interrogates, with some concern, substantial inconsistencies between IOMs activities and the ethos of the GPs. In particular, the chapter is critical of IOMs almost exclusive camp-based focus and its predominant preference for return as a durable solution. Also troubling is an observed decline in IOM references to the GPs as the leading international standards for IDP protection. The chapter finds that IOM adherence with the GPs cannot thus be taken as a given - indeed, adherence to date is likely more by chance than by design.