Butterflies were surveyed as part of the Grassworks project, which investigates the restoration of grasslands in Germany. Data was collected from 187 grassland sites across three regions (Northern, Central, and Southern Germany), each with distinct socio-economic and ecological characteristics. Sampling occurred in 2022 or 2023 and included 40–41 restored grassland sites and 20–25 reference sites (10–12 positive, 10–13 negative) per region with site coordinates reported at two-decimal precision (blurred for privacy). Further included are the hydrology and management of all sites and in case of restored grassland sites also the applied restoration method, starting year of restoration and land use history. The dataset provides detailed information on butterfly species, their abundance and observed behavior surveyed on four 5-m wide and 50-m long sub-transects using Pollard walks for 5 minutes each. If a butterfly was nectar sucking, the nectar plant was also recorded. In addition to transect walks, two active catches for 5 minutes each per site were conducted to assess the species richness of the site more completely. Sampling occurred on four monthly observation rounds between May and August, with an additional observation round in April in the Central region. For each observation round, information on the starting date/time, air temperature, wind speed, cloud cover and observer are provided.