Schools play an important role in promoting student wellness. As directed by the Healthy Hunger-Free Kids Act, the US Department of Agriculture updated the requirements for written school wellness policies in 2016. The WellSAT (Wellness School Assessment Tool) is an online tool that provides a quantitative score for wellness policy comprehensiveness and strength. The WellSAT has been updated 3 times over the past decade to remain current with federal law and best practices. In this article, we describe the process of updating to WellSAT 3.0. The steps included: reviewing the language of each item linked to a federal provision; adding and deleting items based on frequencies from the National Wellness Policy Study and the empirical support for specific policies; gathering feedback from a survey of experts (N = 77) about best practices and measure usability; and establishing intercoder reliability in a national sample (N = 50) of policies. We conclude with recommendations and guidance for the use of WellSAT 3.0.