Complex systems thinking provides a means to reposition and reframe planning’s relationship to theory, interactive learning, the uses of data, and planning’s relationship to the future. We begin by revisiting and re-articulating Rittel & Webber’s “wicked problems” and demonstrate how the complex systems framework acknowledges and builds an understanding around the factors that give rise to such problems. We then explore how to incorporate complex systems thinking in planning by engaging three central practices: incrementalism, communicative/collaborative planning, and Big Data. While Lindblomian incrementalism is sceptical and defensive, complex systems thinking and modelling enables the representation of cross-scale interactions and feedback, allowing for the continual re-examination and revision of both goals (second-order learning) and paths to realizing them (first-order learning). Collaborative planning’s focus on dialogue, debate and deliberation is necessary but not sufficient to address the biophysical, technical, economic or institutional complexity. Complex systems modelling can inform these discursive and deliberative practices with substantive understanding of potential unintended consequences. Our contemporary fascination with Big Data ignores that complex problems are characterized by structural uncertainty rather than data uncertainty. Big Data, like complex systems modelling, is not useful without effective deliberation and rich context. We advocate for incorporating complex systems thinking and tools into existing planning theories and practices to extend their range and reach, and to steer the field away from its historic tendency to fixate on data collection for statistical analyses that ignore the underlying causes of complexity. Planners might want to undertake the considerable effort to learn and engage complex systems thinking and tools if they can integrate, adapt and hybridize them into current planning thought and practice, and make them conceptually accessible, visually powerful, and normatively compelling to both their colleagues and publics.