This article provides an introduction to system dynamics modeling with a particular focus on the use of system dynamics models in political science and international relations. A system dynamics approach offers an alternative to traditional qualitative and quantitative methods by providing a dynamic and endogenous point of view, which allows for understanding the dynamic interactions between variables and making short- and long-term projections for alternative policy choices. This approach is particularly useful to tackle the complex problems of contemporary politics, in which the solutions require combining the insights from different disciplines. Applications of a system dynamics approach in the social sciences cover a broad spectrum, from war initiation and termination to social inequality, from demographics to human development and democratization. This article starts by presenting the brief history of system dynamics models and their use in social sciences, and comparing a system dynamics approach to traditional qualitative and quantitative research methods by discussing the advantages and disadvantages of each one. This discussion is followed by the explanation of the essential components of system dynamics models. Finally, the article provides several applications from international relations via developing models of arms races and spread of intrastate conflicts.