Several government agencies are seeking quality improvement in environmental policy documents by asking for the implementation of Plain Language (PL) guidelines. Our mixed-methods research examines whether the application of certain PL guidelines affects the comprehension and perceptions of readers of environmental policy documents. Results show that the presence of pronouns affects inferential comprehension of environmental impact statement summaries (EIS summaries), but that the effect varies with the reader's education level. Further, headings in question phrasing affect a reader's perception of familiarity and reliability of EIS summaries. A reader's perceptions of EIS summaries and attitudes toward the organizations creating the documents are also affected by overall design features. PL guidelines on the use of pronouns and question headings are not fully supported by our research and need further validation with regard to comprehension. This article ends with a call for further research.