Despite calls for collaborations across animal and human health sectors to control zoonoses, a ‘black-box’ approach to collaborations means there is limited understanding of their drivers, characteristics and dynamics. In this thesis, I develop insights into multisector ‘One Health’ collaborations by examining the case of three zoonotic diseases in two states in India. Over nine months of fieldwork, I interviewed policy actors spread across different sectors, functions and administrative levels, and observed the practices of professionals in the field and in their offices. I used the examples of anthrax, brucellosis and leptospirosis to examine One Health collaborations in the states of Tamil Nadu and Gujarat in India.The identification, measurement and response to zoonoses are complex undertakings requiring specialist expertise. Consequently, discourses and practices around zoonotic diseases are dominated by technical experts. The process of synthesizing and reinterpreting scientific knowledge, in turn, is influenced by politics and power dynamics underlying the experts’ disciplines, sectors and institutions.Across all three zoonoses, I found that it is narratives about diseases, rather than actual disease burdens orrisks, which drive public perception and policy response. The way collaborations ultimately emerge is conditioned by the disease characteristics and is influenced by an interplay of the disease discourses, the political cultures of the state and the practices employed by decision-makers at all levels. In all cases, collaborations do occur, sometimes facilitated by formal guidelines, but very often through everyday practices, in spite of bureaucratic strictures. All cases of collaboration are underpinned by informal networks. Such initiatives, frequently led by middle-level bureaucrats, while responsive to local concerns, are much messier than the processes envisioned in the dominant programmatic literature on ‘One Health’. In order for One Health partnerships to be sustainable, I argue that it is important to develop a nuanced approach to understanding the politics and dynamics underlying multisector collaborations.UK Commonwealth Scholarship, funded by UK Government