This paper describes the findings of a qualitative evaluation of an early years' intervention, I Can's Early Talk (ET) programme. ET was designed to improve speech, language and communication outcomes for children aged 0–5 by focusing on enhancing practitioners' knowledge and skills. The research focused on children aged 3–4 years and was conducted in 14 Sure Start Children's Centres across England, using a combination of observations and interviews with practitioners, centre managers and local authority staff, along with a questionnaire survey of parents. Findings revealed improvements in practitioners' confidence and practice as a result of participating in the programme. The results also suggest that participating practitioners felt their capacity to understand and reflect on how to support children's speech, language and communication improved, particularly in the children's centres which had been accredited for over six months. ET was also found to offer a balance of support and challenge which consolidated and extended good practice and identified areas for development where practice was less effective. In addition, some of the challenges, which characterised and ultimately enhanced the research process, are described.