This chapter introduces System Dynamics (SD) modeling and simulation as a powerful tool to promote systems thinking in the process of policy making and analysis. It proposes an integration of the method with the policymaking process, providing examples of such integration. SD represents a useful systems approach for the analysis of complex social problems and public policies. SD is a systems approach that has been highly influenced by the development of technology, exact sciences, and the application of computer simulation methods to the analysis of complex social science and economic problems. SD was developed in the 1950s by Jay W. Forrester at the Massachusetts Institute of Technology (MIT). The term reference mode refers to patterns of behavior over time. These patterns represent the dynamic behavior of important problem-related variables. The building blocks of causal-loop diagrams are variable names and causal links, which can be either positive or negative.