Regional chapters in the National Climate Assessment (NCA) report provide a comprehensive synthesis of how climate change is impacting United States regions and are extensively used to support climate change decision-making by local communities and policymakers. The regional chapter author teams are tasked with assessing the climate trends, risks, and responses across a range of sectors and across a vast and diverse geography, while making content locally relevant. Regional chapters have evolved in many ways since NCA3, often shifting from focusing on climate stressors and hazards to addressing more diverse human-centric impacts (e.g., human health), inequities, and other barriers to action. The NCA5 author teams were constructed to be intentionally diverse, including more social scientists and cultural practitioners. The objectives of this presentation are to highlight the importance of and advancements in regional chapters in the NCA, reflect on best practices for developing an effective regional chapter, and describe lessons learned and advice to inform future scientific assessments. These observations on the role of regional scientific assessments are particularly timely, given the current uncertainty around federal leadership in completing a national climate assessment. Our recommendations to improve future regional chapters include better coordination with sub-national climate assessments.