Agent-based models (ABMs) are used in the spatial sciences as building-blocks for computer simulation. ABMs have a range of advantageous attributes, not least of which is their flexibility in representing dynamic and highly adaptive physical or human phenomena. ABMs facilitate the exploration of ideas about the myriad of ways that geographical systems develop, behave, interact and evolve, often supporting experimentation with geographical systems in ways that are simply not possible in the real world. Indeed, in many cases, ABMs are developed from the bottom up, pedagogically, as a tool in building theory. Geographers’ work with ABMs has helped to strengthen existing ties with related disciplines such as computer science and informatics, ecology, sustainability science, economics, anthropology, political science and the earth sciences. Primarily because of the value placed on spatial science and behavioral geography in agent-based modeling, work of this kind is helping to infuse geographical perspectives and ‘spatial thinking’ into these fields. This article reviews the development of agent-based modeling in the spatial sciences, its current uses and applications in physical and human geography and potential future trends in its research and development.