Many coasts are eroding. In the Comoros, as in many other small island developing states (SIDS), communities frequently respond to coastal erosion by building seawalls—yet seawalls and other coastal defence structure are controversial, especially in a SIDS context, where they typically are poorly designed and constructed and thus tend to increase rather decrease erosion and are often unable to prevent flooding. Through an exploratory qualitative case study of Grande Comore, the main island of the Comoros (West Indian Ocean), we compare and contrast how local stakeholders, national elites and donors understand coastal erosion and flooding in the context of a changing climate and how they experience and perceive seawalls as a response measure. Our analysis suggests that although stakeholders are aware of different drivers of coastal erosion and flooding, including sand mining, seawalls are a frequent and customary response to coastal erosion and flooding. Little is known about their disadvantages or alternative response measures, especially among local community members. Further, a lack of capacity and resources leads not only to poorly designed and constructed seawalls but also to difficulties in enforcing rules and regulations such as bans on sand mining. From our exploratory study, three conclusions emerge: (1) local drivers of coastal erosion and flooding are more visible than global climate change while funding is more readily available for adaptation to climate change; (2) a mix of context and site-specific measures would be needed to adequately respond to coastal erosion and flooding; and (3) further information and knowledge about the extent and causes of coastal erosion and flooding as well as about the effects of different response measures would be needed to allow such context and site-specific measures.