This dataset provides detailed information on butterfly species abundance and diversity as part of the Grassworks project, which investigates the restoration of species-rich grasslands in Germany. Grasslands are globally threatened ecosystems, and the project aims to identify factors that contribute to successful restoration, focusing on ecological complexity and stakeholder engagement. Data was collected from 187 grassland sites across three regions in North, Central, and South Germany, each with distinct socio-economic and ecological characteristics. Sampling occurred between 2022 and 2023 and included 40 restored grassland sites and 20 reference sites (10 positive, 10 negative) per region. Butterfly abundance and species richness were among the ecological metrics recorded.