Objective: Conduct disorder (CD) involves aggressive and antisocial behavior and is associated with blunted cortisol stress response in male youths. Far less is known about cortisol stress responsivity in female youths with CD or other neuroendocrine responses in both sexes. Although CD is linked to early adversity, the possibility that neuroendocrine alterations may mediate the relationship between early adversity and CD has not been systematically investigated. Method: Within the European FemNAT-CD multi-site study, salivary cortisol, testosterone, the testosterone/cortisol ratio, oxytocin, and psychological stress response to a standardized psychosocial stress test (the Trier Social Stress Test [TSST]), together with common pre- and postnatal environmental risk factors, were investigated in 130 pubertal youths with CD (63% female, 9-18 years of age) and 160 sex-, age-, and puberty-matched healthy controls (HCs). Results: The TSST induced psychological stress in both CD and HCs. In contrast, female and male youths with CD showed blunted cortisol, testosterone, oxytocin, and testosterone/cortisol stress responses compared to HCs. These blunted stress responses partly mediated the relationship between environmental risk factors and CD. Conclusion: Findings from this unique sample, including many female youths with CD, provide evidence for a widespread attenuated stress responsivity of not only stress hormones, but also sex hormones and neuropeptides in CD and its subgroups (eg, with limited prosocial emotions). Results are the first to demonstrate blunted neuroendocrine stress responses in both female and male youths with CD. Early adversity may alter neuroendocrine stress responsivity. Biological mechanisms should be investigated further to pave the way for personalized intervention, thereby improving treatments for CD.