<p>Posttraumatic stress disorder (PTSD) is linked with sexual risk, but less is known about which aspects of posttraumatic psychopathology may be most relevant in these associations. In trauma-exposed adolescents from a national sample (<i>N</i> = 384, <i>M</i>_age =16.4, 72.4% female), we applied a novel “symptomics” approach—which focuses on the role of individual symptoms of psychopathology—to examine associations between PTSD symptoms and two sexual behaviors linked with potential risk: age at first sex and number of recent partners. In relative importance analyses, individual PTSD symptoms explained more variance in these sexual behaviors than did disorder diagnosis. For both sexual behaviors, sense of foreshortened future accounted for the greatest amount of variance; sleep-related symptoms (e.g., nightmares, sleep disturbance) also emerged as relevant. Additionally, dysphoria-related symptoms (e.g., concentration difficulties, anhedonia, restricted affect) explained significant proportions of age at first sex, whereas symptoms capturing trauma-related fear (e.g., intrusions, cued reactivity, hypervigilance) explained variance in number of partners. Findings suggest that select post-trauma symptoms are differentially associated with sexual behaviors in trauma-exposed adolescents. Screening for and intervening on these specific PTSD symptoms may mitigate possible sexual risk in this population, though additional research in larger and more sex-balanced samples is warranted.</p>