In this paper we present the outlines of a geographical approach to cross-border mobility, which in this article we use synonymously with international migration. The approach consists of three constitutive parts that we discern in international migration: people, borders and trajectories. People decide to cross borders or not. In doing so, they can be internationally mobile or immobile, depending on the destination they take into consideration during the decisionmaking process. People follow specific routes to move from one place or region to another, thereby crossing (national) state borders. The approach focuses on whether or not borders act as barriers for opportunities to move. It also pays special attention to the flexibility of the routes and places of destination and settlement. These are not fixed but flexible and migrants' decisionmaking contains aspects of instability, insecurity and volatility affecting their mobility.