Objective: To assess the impact of an online continuing education course on the knowledge, skills, and self-efficacy of nutrition professionals to use an ecological approach to prevent childhood obesity. Design: Quasi-experimental design using intervention and delayed intervention comparison groups with pre/post-course assessments. Setting: Online continuing education course. Participants: Nutrition and health professionals in an online course (n = 105) and a delayed intervention comparison group (n = 37). Intervention: A 6-week, facilitated online course titled, Preventing Childhood Obesity: An Ecological Approach. Main Outcome Measures: Changes in knowledge, skills, and self-efficacy in using an ecological approach to address childhood obesity. Analysis: Paired and independent sample t tests, factor analysis, regression analysis. Results: In contrast to a comparison group, nutrition and health professionals who participated in a 6-week online course had statistically significant increases (P less than 0.01) in their knowledge, skills, and self-efficacy related to using an ecological approach to prevent childhood obesity. Conclusions and Implications: A facilitated online course can be effective at increasing the knowledge, skills, and self-efficacy of community-based nutrition and health professionals in using an ecological approach to prevent childhood obesity in their communities. (Contains 2 tables and 2 figures.)