Resilience has become a popular term in spatial planning, often replacing sustainability as a reference frame. However, different concepts and understandings are embedded within it, which calls for keeping a critical stance about its widespread use. In this paper, we engage with the resilience turn in spatial planning and we dwell on the relation between resilience and sustainability from a planning perspective. Building on insights from ecology, complex system theory and epistemology, we question whether resilience can effectively act as a ‘boundary object’, i.e., a concept plastic enough to foster cooperation between different research fields and yet robust enough to maintain a common identity. Whilst we do not predicate a dichotomy between resilience and sustainability, we argue that the shift in the dominant understanding of resilience from a descriptive concept, to a broader conceptual and normative framework, is bound to generate some remarkable tensions. These can be associated with three central aspects in resilience thinking: (i) the unknowability and unpredictability of the future, whence a different focus of sustainability and resilience on outcomes vs. processes, respectively, ensue; (ii) the ontological separation between the internal components of a system and an external shock; (iii) the limited consideration given by resilience to inter- and intra-generational equity. Empirical evidence on actual instances of planning for resilience from different contexts seems to confirm these trends. We advocate that resilience should be used as a descriptive concept in planning within a sustainability framework, which entails a normative and transformative component that resonates with the very raison d’être of planning.