There has been a surge in scholarship on policy design over the last ten years, as scholars seek to understand and develop existing concepts, theories, and methods engaged in the study of policy design in the context of modern governance. This Element adds to the current discourse on the study of policy design by (i) presenting behavioral assumptions and structural features of policy design; (ii) presenting a multi-level analytical framework for organizing policy design research; (iii) highlighting the role of policy compatibility and policy adaptability in influencing policy efficacy; and (iv) presenting future research recommendations relating to these topics.