Based on attachment theory and a social-cognitive model of posttraumatic stress disorder (PTSD), this study examined the roles of parent–child communication, perceived parental depression, and intrusive rumination in the association between insecure attachment to parents and PTSD among adolescents following the Jiuzhaigou earthquake. In this study, 620 adolescents were recruited to complete self-report questionnaires. The results showed that the direct association between anxious attachment and PTSD was significant, but that between avoidant attachment and PTSD was non-significant. In addition, both anxious and avoidant attachment had indirect associations with PTSD via the mediating effects of parent–child communication openness and problems, perceived parental depression, and intrusive rumination. However, the specific paths between anxious and avoidant attachment and PTSD were different. The findings indicated that insecure attachment among adolescents following the earthquake was predictive for their PTSD, and the mechanisms underlying the association between anxious attachment and PTSD and the association between avoidant attachment and PTSD were distinct. To alleviate PTSD, more attention should be paid to improving the quality of parent–child communication for adolescents with avoidant attachment to parents, and to reducing negative cognition in adolescents with anxious attachment.