Mediterranean wetlands show remarkable seasonal and annual variations in their hydroperiod, i.e. the period during which they are inundated. Climate change-induced hydroperiod reductions have been shown to affect marshland birds but more studies are needed to understand this process in Mediterranean wetlands. The present study shows the demographic response of the Common Reed-warbler Acrocephalus scirpaceus to an unusual and prolonged drought in the Tablas de Daimiel National Park wetland (central Spain). We used data from two constant effort mistnetting stations (2005–2013), and spatially explicit capture-recapture Jolly-Seber models. The Reed-warblers continued reproducing in a dry environment for three years after the start of a dry phase, despite progressive declines in productivity, and ultimately stopped nesting in the fourth year. After the recovery of water levels in subsequent years, the population required another four years to recover a size and productivity similar to those preceding the drought. This situation may be common in the near future given ongoing alterations of the hydroperiod in Mediterranean wetlands as a consequence of climate change and groundwater overexploitation. We also show that spatially explicit capturerecapture models allow the detection of changes in the populations of small passerines, and are an accurate approach to estimating their densities. —Jiménez, J., Hernández, J.M., Feliú, J., Carrasco, M. & Moreno-Opo, R. (2018). Breeding in a dry wetland. Demographic response to drought in the Common Reed-warbler Acrocephalus scirpaceus. Ardeola, 65: 247–259.