The cholera and plague pandemics of the 19th and early 20h centuries shaped Ottoman state-building and expansionist efforts in Iraq and the Gulf in significant ways. For Ottoman officials, these pandemics brought attention to the possible role of Qajar and British subjects in spreading cholera and plague, as well as the relationship between Iraq's ecology and recurring outbreaks. These developments paved the way for the expansion of Ottoman health institutions, such as quarantines, and the emergence of new conceptions of public health in the region. Specifically, quarantines proved instrumental not only to the delineation of the Ottoman–Qajar border, but also to defining an emerging Ottoman role in shaping Gulf affairs. Moreover, the Ottomans’ use of quarantines and simultaneous efforts to develop sanitary policies informed by local ecological realities signal a localized and ad hoc approach to disease prevention that has been overlooked. Ultimately, this study demonstrates that environmental factors operating on global and regional scales were just as important as geopolitical factors in shaping Ottoman rule in Iraq and the Gulf during the late Ottoman period.