This prospective longitudinal study examined two competing models, a traditional social support model and a supportive and detrimental social relations model, to clarify the association of PTSD symptoms with supportive and detrimental social relations. Seven-hundred five adolescents living near the epicenter of the Taiwan Chi-Chi Earthquake participated in the study. The models were evaluated and cross-validated using structural equation modeling. The supportive and detrimental social relations model appeared to be a better fit. After further evaluation of three nested versions of the supportive and detrimental social relations model, detrimental social relations was found to partially mediate the relationship between PTSD symptoms 1 and 2 years following the earthquake. The findings suggest that helping adolescents deal with detrimental social relations can contribute to postdisaster adjustment.