This paper explores the processes involved in developing, embedding and sustaining an ECCE practitioner capacity building programme in the community through an interagency approach, which utilises mentoring and coaching strategies for increased knowledge and skills uptake. There is now conclusive international evidence that early childhood care and education (ECCE) is vital in children's learning and development, and that the benefits are long-lasting, and are more cost-effective than educational investments and remedial interventions later in life. This signifies the importance of high quality ECCE for development and learning, and highlights the potential impact of early childhood intervention programmes. This paper explores the implementation of a quality improvement strategy in seven ECCE centres to improve child-outcomes as part of the Young Knocknaheeny Area Based Childhood Programme (YK). Utilising evidence-based programmes, practitioners from a range of disciplines, working in a low-income community with high levels of adversity, are immersed in an environment of continuous learning in line with best practice implementation science. The core elements of the quality improvement strategy focused on language supports for staff (Hanen Learning Language and Loving It™ training), curriculum enhancement ("HighScope" curriculum training), onsite mentoring for staff, and an Environment Enhancement Fund for each centre. The implementation of a Mentoring Programme involved weekly site visits by a specialist onsite mentor in which the implementation of curriculum content and the suggested environmental changes and teaching strategies were overseen and supported. Pre and post Environmental Rating Scale (ERS) assessments; ITERS-R (crèche) and ECERS-3 (pre-school); showed significant improvements in the quality of ECCE services in the YK catchment area following ECCE practitioners participation in the quality improvement initiative. Pre-school rooms across the seven ECCE centres experienced an overall improvement of +2.5 on the ERS scales, and crèche rooms experienced an overall improvement of +2.4. Approximately 700 children aged 1 to 5 years indirectly benefitted from YK-delivered curriculum and language training programmes in their ECCE settings.