This inquiry examines the personal attribute and environmental factors that contribute to and impede science teacher-leader development. Using a narrative approach, the inquiry focuses on the experiences of three teachers in three different New Zealand primary schools (years 1-6) as they develop in their capabilities as science teacher-leaders during sustained schoolwide science delivery improvement projects. Bronfenbrenner's bio-ecological model and Rutter's views on resiliency are used as a foundation for interpreting the science teacher-leader development process. Teachers identify a variety of personal attribute and environmental factors and the interplay between these factors as risk and supportive factors contributing to and impeding their development as science teacher-leaders. Teachers also identify that their development is influenced by several proximal processes that are context and time dependent. Ramifications of this study in the context of general school curriculum, in particular science development, are also considered.