After the disintegration of the Ottoman Empire, the late 1920s and early 1930s marked a period of consolidation for the newly established nation-states in the Middle East. The introduction of state administration in the desert borderlands and the reinforcement of state borders went along with the tighter regulation of Bedouin tribes and of their cross-border mobility in particular. At the same time, the region was affected by a severe drought, dealing a heavy blow to the Bedouin economy. Scholarship has often analyzed droughts in terms of their one-sided effect on the socio-economic foundations of pastoral communities. The drought of the interwar years has been studied primarily in terms of its contribution to the economic decline of Bedouin tribes. The lack of water and pastures led to heavy losses of livestock. At the same time, emerging border regimes and growing interventionist state politics into tribal affairs restricted Bedouins’ mobility and their ability to compensate for losses by raiding wealthier tribes. By examining the cross-border mobility of Bedouin tribes between Iraq and Syria, this paper, however, provides a more complex picture of the interplay between tribes, states, and ecological factors. Recent scholarship has challenged the seeming contradiction between Bedouin mobility and state control over territory and instead showed their interdependence. Rather than curtailing mobility of tribes, state authorities sought to monitor and channel their cross-border movement. Yet, droughts disrupted patterns of Bedouin mobility, created conflicts over water and grazing land, and thus posed a risk to states in their pursuit of security and control over the borderlands. This paper argues that ecological challenges played as crucial a role as other socio-economic and political factors in determining the course of state-tribal relations and border-making processes in the Middle East during the interwar period. In doing so, it not only considers how the material realities of climate and environment shaped imperial policing of tribes but also how droughts were perceived and used by different actors to assert their own interests. While state authorities exploited the effects of droughts to consolidate state power and reinforce state borders, tribesmen could use periods of drought to demand tax exemptions and cross-border grazing rights. The paper thus ultimately also highlights the role of Bedouin tribes as well as of non-human actors in the formation of the nation-state in the Middle East.