This thesis investigates the implementation of the Smart Green City paradigm and the TwinTransition, understood as the strategic integration of digital technologies and nature-basedsolutions, in the city of Milan. As urban areas face increasing climate-related risks, includingthe Urban Heat Island effect, policy agendas have increasingly promoted the convergence ofdigital innovation and ecological planning to combat it. However, it remains unclear howmunicipal bureaucracies and institutional arrangements shape the practical implementation ofthis transition.Drawing on Urban Assemblage Theory and a qualitative cross-document analysis, this studyexamines the gap between Milan’s strategic climate ambitions and its operational reality. Bycomparing official policy instruments, financial planning documents, and independentmonitoring reports, the research identifies the governance thresholds through which the urbanassemblage is shaped, sometimes stabilizing into more coordinated forms of implementationand sometimes remaining fragmented across disconnected initiatives.The findings show that, although Milan presents an integrated Smart Green City vision at thestrategic level, the implementation of the Twin Transition is constrained by rigid administrativestructures. Regulatory boundaries, weak authority for digital climate data, and separated budgetframeworks limit the cross-sectoral coordination required to connect ecological and digitalinterventions in practice. The analysis further suggests that this fragmentation is reinforced bymismatches between strategic climate plans, urban planning regulations, departmentalcompetences, and the different timescales of ecological planning and municipal budgeting.Overall, the thesis shows that urban climate resilience depends not simply on combining digitaltools and ecological goals, but on whether municipal institutions can coordinate them throughshared authority, aligned instruments, and enforceable implementation mechanisms. In thissense, the Milan case illustrates how fragmentation persists when climate ambition is notmatched by corresponding administrative integration.