The July 22, 2011, Oslo Terror was defined as a national disaster. Former studies on terror attacks and mass shootings have shown elevated levels of posttraumatic complaints both in direct victims and in general populations. Little is known about how such extreme events in a generally safe society such as Norway would affect an adolescent population. This study examines posttraumatic stress reactions and changes in worldview in relationship to risk factors among 10,220 high school students using data from the ung@hordaland survey. One out of 5 respondents knew someone directly exposed, 55.7% experienced the events to some extent as threatening to their own or their close ones’ lives, and 79.9% reported their worldview to be changed. For posttraumatic stress disorder (PTSD) DSM IV criteria, 0.8% reported substantial symptoms of reexperiencing (Criterion B), 4.9% of avoidance (Criterion C), and 1.1% of hyperarousal (Criterion D). Greater personal proximity to the events, higher levels of perceived life threat, and being a female or an immigrant predicted higher levels of PTSD symptom distress. Results indicate that the terror events made a deep impression on Norwegian adolescents, but without causing markedly elevated levels of PTSD symptomatology in the general young population.