Background: Previous research has demonstrated heterogeneous patterns of posttraumatic stress disorder (PTSD) among children following disasters. However, no clear consensus has been reached regarding the postdisaster trajectories of PTSD among children. Objective: The current study examined the trajectories of PTSD among children after exposure to the Wenchuan earthquake and explored potential predictors of distinct PTSD trajectories. Methods: A four-year longitudinal study was conducted to follow 301 children who were evaluated for PTSD symptoms following the Wenchuan earthquake. Trauma exposure and some pre-existing characteristics were measured at four months after the disaster, and PTSD symptoms were measured at 4, 16, 29, 40 and 52 months after the disaster. The trajectories were identified with Latent Growth Mixture Modelling, and the predictors were explored with multinomial logistic regression. Results: The following three latent PTSD trajectories were found among children: resilient (74.9%), relapsing (17.7%) and recovery (7.5%). Trauma exposure was more likely to be related to a more severe trajectory of PTSD, having experienced prequake trauma was more likely to be related to the recovery trajectory and school 2 was more likely to be related to the relapsing trajectory. Conclusion: These findings provide novel insights into children's postdisaster response patterns. Individual heterogeneity existed in posttraumatic reactions. This longer-term longitudinal study captured more detailed and accurate information about the development of these trajectories. Trauma exposure and previous traumatic experience were linked to malignant development of PTSD.