Despite the added value of multisystem (relative to traditional single-system) approaches for characterizing biological processes linked to risk for psychopathology (e.g., neuroendocrine stress responsivity; Buss et al., 2019; Quas et al., 2014), no study to date has evaluated whether multisystem processes may serve as viable biological targets of intervention. Utilizing a multiple-levels-of-analysis approach (Cicchetti & Dawson, 2002), this person-centered study examined whether stress-adapted patterns of hypothalamus–pituitary–adrenal (HPA) axis and sympathetic-adrenomedullary (SAM) system co-activation were amenable to change following the Building a Strong Identity and Coping Skills intervention (BaSICS; Wadsworth et al., 2022). Preadolescents exposed to concentrated poverty (n = 112, Mage = 11.78 years, 57.1% female, 54% assigned to intervention; 40% Hispanic, 63% Black, 20% White) completed questionnaires and the Trier Social Stress Test at both pre- and posttest. Multitrajectory modeling of cortisol and alpha-amylase levels identified four pretest and posttest HPA-SAM co-activation profiles. At pretest, youth exhibiting Asymmetric Nos. 1 & 2 HPA-SAM co-activation reported greater maladjustment relative to youth with Symmetric Nos. 1 & 2 co-activation. Youth exhibiting Asymmetric No. 1 co-activation at pretest were more likely to exhibit Symmetric No. 1 co-activation following BaSICS relative to control. Findings highlight the potential of BaSICS to restore neuroendocrine stress response function in impoverished youth, pointing to HPA–SAM co-activation as a potential biological target of preventive intervention in this population.