The California coast is facing an unprecedented slow-moving danger: sea level rise. Understanding the ability of coastal cities and their decision-makers to adapt to this almost invisible threat is paramount to avoid future damage to both property and lives. Identifying key adaptation barriers, drivers, and lessons is critical to the resiliency of these cities. Analyzing how sea level rise fits on the priority list amongst the most pressing agendas for a city may shed further light on addressing this natural disaster hazard. This qualitative case study performed both in-person and telephone interviews with residents, advocacy groups, and decision-makers in the cities of Newport Beach and San Mateo to identify key adaptation barriers, drivers, and lessons. During and after the interviews, the data was interpreted through a content analysis process. These cities are in different geographical regions along the coast of California that have been deemed vulnerable to sea level rise by the State, and both cities have “high risk” flood zone designations. In Newport Beach, the most vulnerable area is located on Balboa Island, where residents have been hesitant to increase the height of their seawalls to address sea level rise projections and have instead supported the City’s efforts to repair and cap the existing aging seawalls as an interim measure. Unique to San Mateo is that it lies within the most vulnerable county in California to sea level rise. This vulnerability has increased regional collaboration with other jurisdictions in the county and the wider San Francisco Bay Area, which has a history of progressive thinking about climate change adaptation. For these two locations, a broad collective action theoretical framework is used to illuminate how residents, local and regional governments, scientists, nonprofit advocacy groups, and decision-makers comprise a network to adapt to sea level rise. Among the theories tested, network theory played a larger role in explaining how both cities collaborated, used knowledge transfer, and shared perspectives that potentially can be responsive to prompt municipal sea level rise adaptation. Established networks with the ability for capacity building and social learning might lead to greater awareness of the risks of sea level rise. Collaboration through informal and formal relationships, the presence of leaders who advocate for adaptation, and audience-specific messaging may overcome the barriers of skepticism, uncertainty, and partisanship. This dissertation found 17 influences that were frequently mentioned by participants that was thought to drive adaptation, but participant interviews indicated that these influences were found to be insufficient in influencing greater adaptation by decision-makers beyond an incremental approach. In both case studies, this approach resulted in a short-term solution that may result in higher adaptation costs in the future. These cities lack the courage to go beyond an incremental approach and has used the affordable housing crisis, traffic congestion, skepticism, siloed governance, unfunded pension reserves, uncertainty about the projections for sea level rise, and inadequate infrastructure systems as justifications to not engage proactively. Decision-makers have not adequately explored or implemented different adaptation alternatives and chosen to only build incremental upgrades to infrastructure. Monitoring sea level rise and potentially upgrading sea walls or levees sometime in the future is not proactively engaging in adaptive management. There are places, such as the Netherlands and Sacramento region, that have gone beyond an incremental approach, initiating government moratoriums, development restrictions, and providing incentives to property owners to adapt. This dissertation provides findings that will give a deeper understanding of how decision-makers determine whether to adapt to the slow-moving emergency of sea level rise and offers recommendations on how jurisdictions might adapt beyond an incremental approach.