BACKGROUND: Child maltreatment (CM) is robustly associated with youth risk for addictive behaviors, and recent findings suggest that this may be mediated through impulsive discounting of future rewards. However, research indicates that youth self-regulation (emotional and cognitive), particularly in peer contexts, is critical to consider in the study of decision making. This study aimed to examine the indirect link between CM and alcohol and other drug use problems, through delayed reward discounting (DRD), among a community sample of emerging adults. Further, this investigation aimed to examine whether this indirect link was moderated by heart rate variability (HRV), a physiological proxy for regulation of stress reactivity. METHODS: A sample of emerging adults (N = 225; M(age) = 21.56; SD(age) = 2.24; 52.9% female) was assessed at 2 time points, with 1 year between assessments. The sample was comprised of rural emerging adults from lower socioeconomic backgrounds. DRD was examined using a monetary choice task, and HRV reactivity was derived during a social stress task. RESULTS: Increased CM experiences were significantly linked to riskier DRD. HRV reactivity amplified the indirect effect between CM and alcohol use problems via riskier DRD. CONCLUSIONS: The results demonstrate that the connection between CM and alcohol use problems via impulsive decision making is modulated by acute stress response reactivity, as indexed by HRV.