New policy initiatives, such as those concerned with promoting young children's positive mental health, highlight the need for good quality professional education in the early childhood education and care sector. However, although a wealth of literature exists from the school sector, little is known about professional education in early childhood education and care settings. This article presents an analysis of early childhood education and care educators' perspectives about their professional learning during an initiative to promote young children's mental health in 111 early childhood education and care centres in Australia. Questionnaires and feedback forms were collected from educators on four occasions over 2 years. In addition, programme facilitators rated the quality of implementation of the initiative in each centre. Thematic analysis indicated that the professional education was instrumental in building early childhood education and care educators' knowledge about children's social-emotional learning and mental health, increased educators' self-efficacy for mental health promotion and encouraged a more collegial and collaborative workplace. Hierarchical linear modelling supported the learning gains identified in the qualitative analysis, but showed that the effect sizes for positive change depended on the quality of programme implementation. The findings highlight important synergies between opportunities for professional learning and workplaces that are conducive to transformation and renewal. Recommendations from participants for improvement included the need to ensure the relevance of content to local contexts, more extended learning opportunities, translation of unfamiliar language and more accessible timetabling of professional learning sessions. Issues concerning the need to advocate for, and sustain, professional education in early childhood education and care settings are discussed. (author abstract)