Abstract: The theme of the next issue of Urban Planning will be Paradigm Shifts. To make the link between “sustainability” and “paradigm change,” the following commentary analyzes the former concept as a main example of the latter. Although it is often applied to rather modest planning initiatives, “sustainability” can be seen as requiring shifts in cognitive paradigm that are transformational, radical, and not yet fully appreciated by most of those who use the term. Specifically, this term implies a proactive, results-oriented approach (e.g. initiatives to actually meet GHG reduction targets), a long-term viewpoint (e.g. planning for 50 or 100+ years in the future), and a holistic or ecological mindset able to understand dynamic, evolving systems. This last change is the most difficult and requires thinking across scales of action, across time frames, across issue areas and goals (e.g. the “Three E’s” of environment, economy, and social equity), and across communities. It also means integrating different types of actions into a broader program of social change. Though challenging, these cognitive shifts can lead to radically different outcomes than past urban planning.