The psychological impact of a mudslide on survivors of the Wenchuan earthquake in China and the risk factors for development of disaster-related post-traumatic stress disorder (PTSD) were investigated. The study design was cross-sectional and included 1321 survivors who had endured both an earthquake and a mudslide. Participants filled out a self-report questionnaire. One month after the mudslide, the rate of PTSD symptoms was 18.7%. Females, the elderly, those with lower educational levels, those that lacked social support, those who did not take precautionary measures, those living with children below 6 years of age, and those who had higher exposure to traumatic events experienced a higher level of PTSD symptoms. Results indicated that timely rescue, abundant material help, and mental rehabilitation after a disaster play important roles in recovery, and that there are still some high-risk groups that need attention, care, and effective intervention from healthcare professionals and society.