The number of cross-border workers in Luxembourg has steadily increased over the last 30 years. In the collective imagination these cross-border workers come to the Grand Duchy just to work. This paper challenges this representation by measuring the functional integration of cross-border workers in Luxembourg. Using some useful tools linked to the field of Time Geography, it is possible to analyze their activity spaces according to the spatial and temporal organization of their daily activities and trip chains. The spatial distribution and organization of their activities on both sides of the border provide the methodological and analytical support for the findings presented in this paper. The juxtaposition of trip chains with activity spaces allows the identification and characterization of the degree of functional integration of cross-border workers in Luxembourg. Moreover, based on a quantitative survey conducted in three different countries, our results show there are five types of cross-border worker profiles in terms of the degree of integration: commuter-only, home-centered, dispersed, hybrid, and functionally integrated.