Across the globe, governments, industry and educationalists are in agreement that more needs to be done to increase and broaden participation in post-16 science. Schools, as well as teachers, are seen as key in this effort. Previous research has found that engagement with science, inclination to study science and understanding of the value of science strongly relates to a student's science capital. This paper reports on findings from the pilot year of a one-year professional development (PD) programme designed to work with secondary-school teachers to build students' science capital. The PD programme introduced teachers to the nature and importance of science capital and thereafter supported them to develop ways of implementing science capital-building pedagogy in their practice. The data comprise interviews with the participating teachers (n?=?10), observations of classroom practices and analyses of the teachers' accounts of their practice. Our findings suggest that teachers found the concept of science capital to be compelling and to resonate with their own intuitive understandings and experiences. However, the ways in which the concept was operationalised in terms of the implementation of pedagogical practices varied. The difficulties inherent in the operationalisation are examined and recommendations for future work with teachers around the concept of science capital are developed.