The disappearance of migrants, which has reached preoccupying high numbers in recent decades, is related both to the particular vulnerability of migrants traversing dangerous migratory routes and to the high degree of impunity that characterizes investigation and search efforts required. This article argues that the disappearance of migrants at the hands of non-state actors in contexts of systematic impunity and in situations where the state had knowledge or should have had knowledge of a serious risk of such disappearance, but failed to act to prevent it, can be considered to have occurred with the acquiescence of the state. Thus, given that all further elements of the definition of enforced disappearance have been satisfied, this factual situation qualifies as an “enforced disappearance” for the purposes of international human rights law. Key to this demonstration is the concept of knowledge, which is an essential component of acquiescence. This article not only addresses the normative framework of acquiescence and its interpretation by international and regional human rights bodies, including how it relies on the element of state knowledge, but it also examines the extent to which this factor is critical to understanding states’ due diligence obligations to prevent, investigate, and sanction human rights obligations, including disappearances. In order to better understand the factors that should be taken into consideration while assessing a state‘s knowledge of migrant disappearances, including in the context of systematic impunity, it is then suggested to borrow from the international criminal law test related to the concept of “constructive knowledge” and to the doctrine of command responsibility. These considerations should inform a test for assessing whether disappearances of migrants occurring in contexts of systematic impunity can be considered as having been known by the state and as having occurred with its acquiescence and, thus, as constituting “enforced disappearances” under international human rights law.