Panic attacks frequently lead to psychopathological disorders, including panic disorder. Even though panic disorder is a highly comorbid and disabling mental health problem associated with stressful life or traumatic events, perievent panic attacks and their association with panic disorder have hardly been investigated as a central topic after mass trauma. Using data from a longitudinal population-based assessment of Madrid residents after the March 11, 2004 train bombings (N = 1,589), with assessments conducted 1, 6, and 12 months after the attacks, the rate of perievent panic attacks was 10.9%. Level of exposure, previous life stressors, and negative emotionality were associated with perievent panic attacks (β = .12, .15, and .10, respectively), which in turn mediated the relationship between exposure to the terrorist event and panic disorder in the following year. Previous life stressors (β = .15) and low social support (β = -.14) were directly associated with panic disorder during the subsequent year. The most vulnerable individuals who experienced perievent panic attacks were 3.7 times, 95% confidence interval [CI] = [2.1, 6.4], more likely to suffer from panic disorder in the following year. Results suggest that early identification of perievent panic attacks following mass trauma may be helpful for reducing panic disorder.