We organized a Special Interest Meeting on “Formalizing knowledge in clinical and health psychology” in June 21th-22th, 2023. The main goal of this meeting was to bring together researchers who are active in the different ways of formally representing knowledge in psychology. Formally representing knowledge is increasingly used in health psychology and clinical psychology, amongst these are knowledge graphs, semantic networks, (causal) Directed Acyclic Graphs and ontologies. All have in common that conceptual and theoretical knowledge is made precise, explicit, and formalized. Formalizing our knowledge has several advantages: (1) providing precise definitions of concepts and constructs, (2) improving our measurement of constructs, (3) making theory-based hypotheses and their underlying assumptions explicit and transparent, and (4) facilitating the sharing of knowledge towards researchers, practitioners and policy-makers. Formal ways to represent knowledge are the next steps in our science, and will also create dialogue, interaction and synergy with other disciplines. In this meeting the focus was upon • formal ways to represent and visualize knowledge • causality and causal inferences • innovation in measurement of constructs • network analyses • single case approaches