Border walls have recently proliferated and become a global phenomenon with about a third of the countries having at least one wall or fence along its borders. This trend contrasts the idea of the global village and fits into a trend towards deglobalization. So far little attention has been given to their unintended effect. This article fills this gap by developing a gravity model for the years 1990-2014 regarding 118 countries, 44 (37%) of which had a wall during the research period. The impact of border structures on cross-border trade is economically and statistically significant. Countries separated by a wall trade on average 4 to 73 percent less than would ceteris paribus be the case if the border wall did not exist.