Hospital access block, often referred to as Emergency Department (ED) overcrowding when it manifests there, is an important public health issue and seemingly intractable problem in our evolving healthcare systems. 1 The multiple, dynamic, and interdependent factors influencing its cause (and potential solutions) may best fit a complex adaptive systems (CASs) analysis and approach. Complex adaptive systems differ from simple systems in the number of components, the degree of interconnectedness between and among those components, and the certainty of a working solutions. Complicated systems lie some place in the middle but would still operate with predictable and controllable characteristics. While this categorization itself may be an oversimplification, it is clear that simple/complicated systems have different properties (linear cause-and-effect, predictable outcomes), and behave differently than complex systems (non-linear and difficult to predict). 2-4 These different properties have a significant impact on problem formulation and solving. In fact, not recognizing how complex systems behave has limited attempts at health system "transformation" 5 and complex issues management. 6 For example, our approach to the opioid crisis 7 and the obesity crisis 8 started with siloed and doomed-to-fail linear approaches but have now recognized the complexity of the problem. 9 This suggests that we need to shift our mindsets, and improve our systems thinking, as we address the health system problems that have proven resistant to conventional approaches. These shifts in thinking may significantly impact a Health System's approach to ED access block. 10 Understanding the number of components and degree of inter-dependencies in the system may bring to the fore previously under-emphasized, or even unrealized, strategies and solutions.