Beckwith-Wiedemann syndrome (BWS) is a generalized overgrowth condition as well as regional and organ overgrowth in newborn children. It includes an increased risk of certain embryonal tumours. The aetiology of BWS is complex as different genetic and epigenetic alterations at chromosome region 11p15.5 may occur. We report the first case of paternal uniparental disomy in Beckwith-Wiedemann syndrome in Iceland. The diagnosis of Beckwith-Wiedemann syndrome is important as the risk of malignant tumors makes it mandatory that the children are followed for several years with regular investigations to detect the tumors as early as possible.