Nutrient warnings, including warnings on packaged foods and restaurant menus, can be used to show when a food or drink has high levels of calories or unhealthful nutrients like sodium, saturated fat, and added sugars. As of December 2021, calorie and nutrient warnings (including for sodium, saturated fat, and sugar) are required on packaged food and beverage labels in five countries (Chile, Peru, Uruguay, Mexico, and Israel) and similar laws have passed but are not yet implemented in three additional countries (Brazil, Colombia, and Argentina). This fact sheet reviews relevant, scientific literature on nutrient warnings for a science and policy audience. Overall, evidence from randomized controlled trials and real-world studies suggests that nutrient warnings can increase consumers’ understanding of the healthfulness of foods and have the potential to play a role in reducing purchases of foods and drinks high in calories, sodium, and added sugars. To maximize public health impact, policymakers should design nutrient warnings to be simple, highly visible, and convey information with shapes, icons, and other imagery in addition to text.