Background Sex differences in youth's posttraumatic stress disorder (PTSD) symptomatology have not been well studied. Methods Based on a recently burgeoning theory of psychopathology networks, this study conducted sex comparisons of global and local connectivity of PTSD symptoms in a sample of 868 disaster-exposed adolescents (57.0% girls; a mean age of 13.4 +/- 0.8 years) with significant PTSD symptomatology evaluated by the UCLA PTSD Reaction Index for DSM-IV. Results The results revealed that global connectivity was stronger in girls' network than in boys', and individual symptoms' connectivity and its rankings differed by sex. Intrusive recollections, flashbacks, avoiding activities/people, and detachment were the most strongly connected symptoms in girls, whereas flashbacks, physiological cue reactivity, diminished interest, and foreshortened future were the most strongly connected symptoms in boys. Several symptoms were identified as featuring large connectivity differences across sex. Conclusions These findings provide novel insights into sex differential risk and features of youth's PTSD symptomatology. Sex differences reflected in the co-occurrence of PTSD symptoms may merit more consideration in research and clinical practice.