This paper presents a new DSS Design Model for complex, mission critical decision-making situations and its technical, conceptual, and partial empirical evaluation. The new model was derived from conceptual design research and through a deep qualitative field research study at an electric power utility control center—a typical arena for “wicked” problems. The model suggests an iterative process of theory, simulation, and decision-making interactions. The DSS Design Model is validated using a tool instantiation, microgrid mini-case, and current research of a KMDSS for telecommunications. Main findings suggest that broader and more integrated approaches are necessary to design DSS for complex domains.