This study evaluated the effectiveness of an online short course based on the Health Promoting Schools Framework and specifically designed for Early Childhood Education and Care (ECEC) professionals. The short course aimed to enhance ECEC professionals' nutrition knowledge, confidence, role legitimacy and adequacy to model healthy behaviours, teach healthy food habits and create health-promoting environments. Participants (n = 116) working at Australian ECEC services were assigned to control (n = 62) or intervention (n = 54) groups. Both groups completed a pre-intervention survey. The intervention group accessed the four-week course and completed the post-intervention survey. The control group completed a second survey after four weeks but before accessing the course. Statistical analyses revealed significant positive changes in confidence, nutrition information utilisation and role perception for the intervention group. This study's findings suggest that evidence-based online nutrition training could be used to improve ECEC professionals' practice to foster better nutrition outcomes for young children.