The moths of the marshlands around lake Pfäfikon (canton of Zurich). - Nocturnal Lepidoptera contribute substantially to insect diversity. Furthermore, many have highly specific habitat requirements and may thus be useful as bioindicators. However, they are often overlooked due to their inconspicuous life style. I studied the diversity of primarily nocturnal Lepidoptera around lake Pfäffikon (Zurich Oberland) from 2011 to 2013. I recorded a total of 288 species, 47 of which are characteristic wetland specialists and largely restricted to peat bog and marshland habitats. Twenty-eight of the observed species are endangered. The number of specialized and endangered species is exceptional compared to that of eighteen other marshland and peat bog areas in Switzerland; furthermore, many of the species around Lake Pfäffikon are found in relatively high numbers. The results of this study emphasize the significance of the nature protection areas around lake Pfäffikon as important habitats for nocturnal Lepidoptera and should be taken into consideration for both management activities and the definition of conservation goals.