Eradication of the neophyte Himalayan Balsam (Impatiens glandulifera) was a successful joint project of two bordering national parks Thayatal (AT) and Podyjí (CZ) that led to a significant decrease of Himalayan balsam plants in the river valley and return of native plants. The most important success factors were the common approach to river valley management, access to both river banks by Czech staff, change in management of river valley meadows, and ongoing joint monitoring in the river valley.