This study explores the development and implementation of a professional development intervention for teachers in data-use as part of a whole school self-evaluation (SSE) process. A review of literature relating to professional development in general and data-use in particular informs the key features of the intervention which is tested in five Irish post-primary schools. The intervention involves a university-based expert in SSE, working directly with SSE teams in each of the five schools to develop a data-informed school improvement process over the course of an academic year. Participants in each school are facilitated to establish an SSE team, gather and analyse data, set targets, complete a self-evaluation report and a school improvement plan. A conceptual framework for the evaluation of the intervention is presented. As such, the evaluation focuses on the core and structural features of the intervention, and changes in teachers' knowledge, skills and attitudes with regard to data-use following the intervention. The findings highlight features of the intervention that supported teachers' professional development in data-use, limitations of this approach as well as the learning that occurred for the teachers involved.