Objective:The COVID-19 pandemic highlights the public's need for quality health information that is understandable. This study aimed to identify (1) the extent to which COVID-19 messaging by state public health departments is understandable, actionable, and clear; (2) whether materials produced by public health departments are easily readable; (3) relationships between material type and understandability, actionability, clarity, and reading grade level; and (4) potential strategies to improve public health messaging around COVID-19.Methods:Based on US Centers for Disease Control and Prevention statistics from June 30, 2020, we identified the ten states with the most COVID-19 cases and selected forty-two materials (i.e., webpages, infographics, and videos) related to COVID-19 prevention according to predefined eligibility criteria. We applied three validated health literacy tools (i.e., Patient Education Materials Assessment Tool, CDC Clear Communication Index, and Flesch-Kincaid Grade Level) to assess material understandability, actionability, clarity, and readability. We also analyzed correlations between scores on the three health literacy tools and material types.Results:Overall, COVID-19 materials had high understandability and actionability but could be improved in terms of clarity and readability. Material type was significantly correlated with understandability, actionability, and clarity. Infographics and videos received higher scores on all tools.Conclusions:Based on our findings, we recommend public health entities apply a combination of these tools when developing health information materials to improve their understandability, actionability, and clarity. We also recommend using infographics and videos when possible, taking a human-centered approach to information design, and providing multiple modes and platforms for information delivery.