Educators are at the heart of educational reforms, such as the introduction of mental health promotion initiatives into early childhood education and care (ECEC) settings. Good quality implementation of reforms requires educators to engage in high quality professional learning: If educators have not had opportunities to gain appropriate knowledge and expertise, new initiatives may be poorly implemented and may consequently achieve limited outcomes. This article reports ECEC educators' perspectives about the impact on their knowledge and practices of the professional education component of the KidsMatter mental health promotion initiative. Educators from 111 ECEC services across Australia contributed a range of types of data, including questionnaires about their knowledge and self-efficacy, feedback about each professional education session, and photo stories about their changed professional practices. Participants indicated that their professional learning led to changed practices in areas such as interpreting children's behaviours, interacting with children, approaching parents, and collaborating with colleagues. Participants' photo stories illustrate how professional education that focuses on content, active learning, coherence, and collaboration can positively influence knowledge and practices. However, if such gains are to last beyond relatively highly resourced start-up phases of initiatives, professional education needs to integrate with, and draw from, the ongoing availability of other professionals such as guidance and counselling staff, who have complementary knowledge and expertise; be recognised and embedded as a core component of ECEC educators' roles and their workplace practices; and be culturally and contextually situated. Staff accounts of the impact of their professional learning on their practices can highlight to policy-makers the practical outcomes of strong investments in professional education. Awareness by other professions of the affordances and constraints faced by ECEC educators may contribute to interdisciplinary synergies among the range of professions involved in mental health promotion in educational settings.