There is general agreement that Geographical Information Systems (GIS) have a place within the geography classroom; they offer the potential to support geographical learning, exploring real-world problems through student-centred learning, and developing spatial thinking. Despite this, teachers often avoid engaging with GIS and research suggests that the lack of GIS training in initial teacher education is partially to blame. In response to this, this article explores how 16 trainee geography teachers were supported to develop their use of GIS across a one-year, postgraduate teacher training course in England. The project, an interpretive case study underpinned by a constructivist epistemology, used questionnaires and interviews to elicit trainees' understandings of the nature of GIS, and to explore their engagement with it across their training year. Results suggest a programme of embedded training developed in trainees a more nuanced understanding of the value of GIS for supporting geographical learning and, thereby, increased self-efficacy towards and engagement with it in their teaching practice. However, not all trainees embraced GIS as a pedagogical tool and the study raised several key issues for geography teacher education, including the knowledge culture within schools in the teacher training partnership, and the importance of trainee self-efficacy towards GIS.