Background: Sun exposure, especially during childhood, is the main environmental risk factor for skin cancers. This study evaluated the impact of the school-based sun safety education program "Living with the Sun" on the knowledge and behavior of primary school children regarding sun safety in Reunion Island. Methods: This multicenter, comparative intervention study was conducted in selected primary schools of Reunion during the 2016-2017 school year. The intervention consisted of an in-class slide-show presentation on sun safety, a teaching guide, and school trips during which children were offered sunscreen and were requested to wear sunglasses, a T-shirt, and a cap. The children completed a questionnaire before and after the intervention. The percentage of children wearing a cap in school playgrounds at the end of the school year was compared between paired intervention and control schools. Results: Seven hundred children from 7 Reunionese schools completed the questionnaire before and after the intervention. There was a statistically significant improvement in children's knowledge of sun safety, with differences between schools, teachers, school levels, and questionnaire responses. The percentage of children wearing a cap at the end of the school year was significantly higher in intervention schools compared to control schools. Conclusions: Children's knowledge and behavior regarding sun safety improved significantly as a result of the intervention.