Rationale, aims, and objectives: How to clarify the implications of complexity thinking for decision making in the intensive care unit (ICU)?. Method: Retrospective qualitative empirical research. Practitioners in an ICU were interviewed on how their decisions were made regarding a particular patient in a difficult, clinical situation. Transcriptions of these interviews were coded and retrieved in Maxqda, a software program. Assisted by complexity thinking, researchers focused on the decision-making process and the shift from analytic approaches to complex approaches. Results: Originally, practitioners took their decisions with negligible transdisciplinary interactivity, drawing on analytical knowledge. Later on, they shifted to transdisciplinary practices, paying attention to more participation in their decision-making processes within their complex environment. Conclusions: Complexity thinking demonstrates that this is a better model towards understanding transdisciplinary decision making then most analytical methodologies.