Several attractive tourist regions in the Czech Republic are located in border areas, making them accessible to visitors from the other side. Although the Czech Republic has been a member of the Schengen area since 2007 and border controls have since been abolished, the border is still present, for example, in non-connected public transport, insufficient cross-border infrastructure, or in tourists' preferences for accommodation. These factors contribute to unsustainable forms of tourism in border areas, manifested by large numbers of day visitors arriving by private cars. The paper analyzes the topic of the Czech-Polish border, using semi-structured interviews with tourism actors (cities and municipalities, entrepreneurs, and NGOs). The results show that after 1945, the Czech-Polish border was re-bordered for political reasons, and cross-border contacts also suffered due to population exchanges on both sides. A strong border effect is still present, which may lead to overtourism in some famous places without adequate financial benefits for the affected destinations. The paper concludes by presenting recommendations on how to mitigate the border effect in tourism and thus contribute to the sustainability of tourism in the region.