Despite its relative newness, entrepreneurial ecosystems (EEs) have attracted much attention from research and policy but they are recognized to be largely untheorized. It is claimed that one aspect which distinguishes the EE perspective from other perspectives related to business environments is its systemic approach; however, much of the systemic approach still needs to be investigated. The aim of this paper is therefore to investigate how the systemic and complex approach of EEs can be theoretically strengthened. We do this by investigating what values complex adaptive system theory holds for advancing the EE perspective. We highlight four propositions which are of particular importance for strengthening the systemic approach of EE: spatial and component boundaries of the system; self-governance; the relational dimension between system components and the system; and the evolution of the system. We propose that boundaries should be seen as a natural part of the system, that a complex system is too complex to capture all components and all interactions, and that studying only individual activities will not enable us to fully understand the system's behaviour.