Objective This article examines the impact of disasters on social capital in the context of Hurricane Katrina. Method One hundred eighty‐two counties affected by Hurricane Katrina are included in the study. Disaster‐related data, social capital, and community characteristics of these counties three years before and three years after the disaster are analyzed using a longitudinal fixed‐effect model. Results Hurricane Katrina slowed down the growth of social capital, but growth gradually recovered following the disaster. After controlling for community characteristics, areas that received more federal government assistance experienced stronger growth in social capital post‐Katrina. Additionally, metropolitan areas with a higher percentage of senior population, higher ethnic diversity, more per capita housing units, and lower population density appear to have had higher levels of social capital. Conclusion Disasters could hinder the growth of social capital and federal disaster assistance could potentially alleviate the negative impact.