The concept of resilience is currently being widely promoted and applied by environmental and development organizations. However, their application of resilience often lacks theoretical backing and evaluation. This paper presents a novel cross-fertilization of two commonly used approaches for applying resilience thinking: the grassroots movement of Transition Towns and the Resilience Alliance's Resilience Assessment. We compared these approaches through a text analysis of their key handbooks and combined them in a series of participatory workshops with a local partner active in the Transition Movement. Our results demonstrate that despite sharing a number of key features, these two approaches have complementary strengths and weaknesses. Strengths of the Transition Movement include its motivating overarching narrative of the need to transform in response to global sustainability challenges, as well as practical tools promoting learning and participation. The Resilience Assessment's conceptual framework and structured process generated context-specific understanding of resilience, but provided little guidance on navigating transformation processes. Combining the Resilience Assessment's theory on complex systems with the Transition Movement's methods for learning also generated synergies in fostering complexity thinking. Based on these findings, we believe that integrating strengths from both approaches could be widely useful for practitioners seeking to apply resilience for sustainable development. Our study also highlights that methods for assessing resilience can be improved by combining insights from science and practice.