Introduction: schoolchildren are estimated to be among the most vulnerable to the negative effects of natural disasters. One of the most common consequences is post-traumatic stress disorder (PTSD). This study evaluated PTSD symptoms in schoolchildren affected by an earthquake and tsunami in Chile. Method: a total of 325 schoolchildren aged 10 to 15 years (52,6 % female and 47,4 % male) participated 12 months after the natural disaster. Of this population, 167 schoolchildren were exposed to the earthquake and tsunami, and 158 children served as a comparison group, as they lived more than 360 km from the epicenter. Results: the groups showed statistically significant differences in the proportion of schoolchildren with PTSD (p < 0,05): 13,9 % in the non-exposed group and 29,9 % in the group exposed to the natural disaster. The association between group membership and PTSD was also statistically significant (χ2(1,325) = 12,08, p < 0,001, V = 0,19) at 12 months. Conclusions: schoolchildren exposed to the earthquake presented greater PTSD symptoms than the comparison group. Therefore, symptom severity could be determined by the level of earthquake exposure. The study findings propose an understanding of the processes that contribute to addressing mental health in school education.