The climate transition poses major challenges for urban areas, which make a considerable contribution to greenhouse gas emissions and are often poorly adapted to climate change. Concepts such as urban sustainability, climate urbanism, and urban climate governance are urban climate discourses that adapt the broader climate transition to the urban scale and can be grouped under the Urban Climate Transition (UCT) discourse. Our research asks whether and how the UCT discourse is institutionalised into urban policy and practice. This question is crucial because it is at the urban scale that the climate transition discourse manifests materially through policies on planning, transport and energy, inter alia. Approaches to understanding the institutionalisation of ideas, narratives, imaginaries, and discourses have recently gained traction in urban planning. Cultural Political Economy is one such approach that is concerned with the relationship between semiotic (imaginaries, discourses) and extra-semiotic (material) factors. This research stems from the Urban Retrofit project which investigates place-based adaptations to the built environment through planning and development systems. Within this project we mapped governance structures and policy processes for five secondary UK cities, setting out how the urban climate transition features, and supplemented this with 21 interviews with key policy actors. Our analysis identified factors enabling and constraining the institutionalisation of the urban climate transition along lines of enquiry drawn from Cultural Political Economy that encompass the coherence of the UCT as an imaginary, its interaction with rival imaginaries such as housing development, and material factors such as governance organisation and funding mechanisms.