This research aimed to evaluate the interdisciplinary educational intervention effects on knowledge of eating, nutrition, and physical activity in elementary-school students. Participants were 368 school children enrolled in public schools. The research was organized in three stages: pre-intervention, intervention and post-intervention. In pre-intervention, children were evaluated regarding their nutritional status. They also answered questionnaires related to eating and nutrition and physical activity. In the intervention stage, educational interventions were carried out on the same topics for a period of five months; in post-intervention, children answered the same questionnaires applied in pre-intervention. Despite most children having normal nutritional status (58.2%), a high number of students were overweight (38%). In the initial phase, it was found that most children had excellent knowledge of eating, nutrition, and good physical activity knowledge (p-value < 0.05). Educational health intervention significantly increased children’s knowledge of eating, nutrition, and physical activity, when evaluated in the post-intervention period. Both boys and girls increased their knowledge of eating, nutrition, and physical activity after the application of interdisciplinary interventions (p-value < 0.05). A similar effect was observed for children with different nutritional status. It is concluded that interdisciplinary educational interventions carried out for children in an elementary-school environment are effective for improving knowledge of eating, nutrition, and in physical activity, promoting healthier habits among children.