This study aimed to estimate the prevalence of posttraumatic stress disorder (PTSD) and to identify associated risk factors among migrant workers 4 years after the 2008 snowstorm in China. A cross-sectional survey of 528 respondents was conducted to collect data in Changsha, the capital of Hunan Province. A multistage cluster sampling method was applied in selecting subjects from migrant workers’ gathering areas. Association between the independent variables and PTSD was analyzed using logistic regression analysis. The prevalence of PTSD was 17.42% among migrant workers in Changsha. Being male, being older than 35 years, being an electrician, having dependent children, suffering property damage, being without medical insurance, and having low social support were risk factors significantly related to the development of PTSD. Effective and sustainable mental health services should be directed particularly to the migrant workers, who are among the groups most vulnerable to the direct impact of snowstorms.