Objective. This study mainly aimed to explore the association between brain-derived neurotropic factor (BDNF) Val66Met polymorphism and posttraumatic stress disorder (PTSD) among flood survivors in China. Methods. Individuals who experienced the 1998 Dongting Lake flood in Southeast Huarong, China, were enrolled in this study. Qualified health personnel carried out face-to-face interviews with participants. PTSD was identified using PTSD Checklist-Civilian version (PCL-C). Blood samples were collected from the participants to extract DNA for genotyping. Results. A total of 175 participants were enrolled in this study. The prevalence of PTSD among flood survivors at 17-year follow-up was 16.0% (28/175). Individuals with PTSD were more likely to be female, experience at least three flood-related stressors, experience at least three postflood stressors, and carry the Met than those without PTSD. Compared with Val/Val homozygotes, Met carriers had higher scores of PCL-C (mean ± standard error: 23.60±7.23 versus 27.19±9.48, P<0.05). Multivariable logistic regression analysis indicated that Met carriers (aOR = 4.76, 95% CI = 1.02–22.15, P<0.05) were more likely to develop PTSD than Val/Val homozygotes. Conclusions. Met carriers for BDNF rs6265 are at higher risk of developing PTSD and also exhibit more severe PTSD symptoms than Val/Val homozygotes among flood survivors in China.