The Family Bereavement Program (FBP) is a family-based intervention for parentally bereaved children and surviving caregivers. Results are reported of a randomized controlled trial, examining intervention effects on emotional reactivity and regulation of young adults who participated in the program 15 years earlier. Participants (N = 152) completed four emotion challenge tasks: reactivity to negative images, detached reappraisal while viewing negative images, positive reappraisal while viewing negative images, and reengagement with positive images. Outcomes included cardiac interbeat interval (IBI), pre-ejection period (PEP), and respiratory sinus arrhythmia (RSA) as well as self-reported emotional experience and regulation effectiveness. Direct intervention effects and effects mediated through improved parenting were estimated. Several significant effects were observed in primary analyses; however, none remained significant after correction for familywise Type I error. Parenting mediated FBP effects on IBI during negative reactivity (b = 15.04), and on RSA during positive reengagement (b = 0.35); the latter effect was accounted for by changes in breathing. Intervention condition was a direct predictor of self-reported detached reappraisal effectiveness (b = 1.00). Intervention and gender interacted in predicting self-reported negative emotion during the negative reactivity (b = 1.04) and positive reappraisal tasks (b = 1.31) such that intervention-condition men reported more negative emotions during those tasks. Although these findings should be considered preliminary given the limited power of the corrected statistical tests, they suggest long-term effects of family intervention following the death of a parent on offspring's emotional reactivity and regulation ability that should be pursued further in future research.