Design, implement, and evaluate the effectiveness of a video-based online training addressing prenatal nutrition for paraprofessional peer educators. Quasi-experimental pre-posttest study with 2 groups of paraprofessionals working for the Expanded Food and Nutrition Education Program in 17 states and US territories: intervention (n = 67) and delayed intervention comparison group (n = 64). An online training was systematically developed using Smith and Ragan's instructional design model, the Cognitive Theory of Multimedia Learning, principles of adult learning, and selected constructs of the Social Cognitive Theory. Changes in knowledge, identification of inappropriate teaching practices, and self-efficacy, were assessed. Within- and between-group comparisons were done using ANCOVA. The intervention group scored significantly higher (P <.05) in all evaluations compared with preassessments and the comparison group. After delayed intervention, the comparison group scored significantly higher (P <.05) than in preassessments. Paraprofessionals reacted positively to future online trainings and were interested in them. A video-based online training is an effective method to complement in-person trainings to prepare paraprofessionals to teach nutrition lessons.