In this paper we explore the views and opinions of four secondary education science teachers regarding the teaching of scientific competences. Their views were gathered in the context of a training programme in which they had to design, implement, and assess their own teaching unit for developing students' scientific competences by means of context-based learning. Analysis of the data yielded a set of 14 categories distributed across 5 areas: scientific competence and context-based teaching; the teacher and his/her professional environment; implementation in the classroom; development of the teaching unit; and assessment. This process also identified the aspects which teachers believed either facilitated or acted as an obstacle to the development of scientific competences through context-based teaching. We discuss the implications of our findings and suggest ways in which a shift towards a context-based approach to teaching scientific competences can best be achieved, and consider a series of factors related to teachers' professional identity that may influence this process.