The transition to net-zero emission urban bus (ZEB) systems is receiving increased attention in research and policymaking. Most studies in this area focus on techno-economic aspects and the views of a narrow group of stakeholders. This offers limited insight into the range of barriers that constrain transitions in real-world contexts. This article offers a political-economic and multi-stakeholder perspective on the technical and non-technical barriers to ZEB transitions within the UK context. It develops a theory-guided empirical case study, informed by stakeholder theory perspectives and semi-structured interviews with stakeholders in the local bus transportation system. It finds that a transition to net zero will require addressing technical, policy, market, and cooperative barriers across sectors and policy levels. On the one hand, this relates to high costs and performance uncertainties over ZEB technology and infrastructure. On the other hand, it concerns unsustainable bus networks from passenger patronage and coordination perspectives, stakeholder cooperative gaps, and high car use and dependency in urban areas. Policy portfolios and stakeholder collaborations, beyond a ‘net-zero’ and sectoral focus, could tackle barriers to system-level change. Further application of the theoretical framework can contribute to a broader body of knowledge about transition barriers operating in different political and economic contexts.