We assessed whether active dissemination of the North American Guidelines for Children's Agricultural Tasks (NAGCAT) reduced childhood agricultural injuries. In this randomized controlled trial, lay educators visited intervention farms to review NAGCAT. New York State farms with resident or working children were randomized. Control farms were visited only to collect baseline data. Data on childhood injuries, tasks, and hours worked were obtained quarterly for 21 months. Injury rates per farm were compared between the treatment and control groups, along with time span to occurrence of an injury and to violation of NAGCAT age guidelines. Intervention farms were less likely than control farms to violate NAGCAT age guidelines in the areas of all-terrain-vehicle use and tractor and haying operations. Cox proportional hazards regression models showed a significant protective effect of the intervention on preventable injuries after adjustment for important covariates. Our results showed that dissemination of NAGCAT reduced rates of work-related childhood agricultural injuries. A comprehensive public health approach is needed to reduce non-work-related childhood injuries.