The Helgoland mud area in the German Bight is one of the very few sediment depocenters in the North Sea. Despite the shallowness of the setting (< 30 m water depth), its topmost sediments provide a continuous and high-resolution record allowing the reconstruction of regional paleoenvironmental conditions for the time since ∼400 A.D. The record reveals a marked shift in sedimentation around 1250 A.D., when average sedimentation rates drop from >13 to ∼1.6 mm/year. Among a number of major environmental changes in this region during the Middle Ages, the disintegration of the island of Helgoland appears to be the most likely factor which caused the very high sedimentation rates prior to 1250 A.D. According to historical maps, Helgoland used to be substantially bigger at around 800 A.D. than today. After the shift in sedimentation, a continuous and highly resolved paleoenvironmental record reflects natural events, such as regional storm-flood activity, as well as human impacts at work at local to global scales, on sedimentation in the Helgoland mud area.