Food-energy-water (FEW) nexus governance includes the communication and collaboration among multi-level stakeholders across sectoral boundaries of the resources for decision-making. It can increase resource security and decrease unintended consequences, as compared to single-sector governance approaches. Despite these benefits, in practice, many decisions continue to be made separately from one another without cross-sector collaboration. This research integrates the theory of collaborative governance with the concept of the FEW nexus to identify and understand the barriers to this collaboration and to provide recommendations for increased collaborative FEW nexus governance. Focusing on the Phoenix, Arizona metropolitan area, a water-scarce region with a growing population, we conduct a comprehensive case study with social network analysis, participant observation, and interviews. We present the results of our analysis in three sections. First, we identify the key barriers to collaborative FEW nexus governance within four identified themes: structural asymmetries, process asymmetries, communication and coordination, and external influences. Second, we unpack how stakeholders in our study case experience these barriers. Finally, from our case study, we provide recommendations for overcoming barriers and implementing collaborative FEW nexus governance in practice, such as building trust and finding mutual benefit. We conclude that “sector mismatch,” similar to scale mismatch, is the main cause of the identified barriers and that approaches to collaborative FEW nexus governance must address this mismatch for successful engagement.