This study aimed to evaluate the feasibility, acceptability and effectiveness of the Connecting the Dots (CTD) professional development program for primary health professionals (PHPs). CTD embedded key messages from the Healthy Beginnings early childhood obesity prevention program into online webinars delivered by Karitane, a not-for-profit parenting service. The evaluation used an action research approach, including both process and impact evaluation. Process evaluation included webinar observations to identify behaviour change techniques and adult learning strategies used by facilitators, and acceptability surveys after webinars. Impact evaluation examined changes in PHPs’ knowledge, attitudes, practices and self-efficacy using repeated surveys before and one month following webinars. Interviews with attending PHPs and program facilitators informed process and impact evaluation. From June 2022 to June 2024, CTD delivered 36 webinars, 1,246 PHPs registered and 463 attended live. Facilitators' delivery style reflected adult learning principles, and they used behaviour change techniques that would be expected to influence PHPs’ knowledge and skills. The national scope of the program was seen as a strength but posed challenges for dissemination; facilitators reflected on the difficulty of reaching and meeting the needs of a national audience. Acceptability surveys indicated that >90% of PHPs viewed the program favourably; this was echoed in qualitative reflections. PHPs valued practical advice, interactivity of webinars, and provision of program materials to review after sessions. Impact evaluation findings suggested the program supported the development of knowledge and awareness of early childhood health promotion; however, interviewees offered few reflections regarding their clinical application of the content. In future, similar programs should include a more comprehensive impact evaluation, including an examination of changes to clinical practice and child health outcomes. The findings also highlight the need to ensure appropriate investment in promoting such programs to ensure successful scale-up.