Our nation is experiencing historic rates of drug overdose deaths that has left behind millions of bereaved families. People who are bereaved by overdose experience a “special grief” that includes guilt, shame, and blame for their loved one’s death that often compounds suffering and help-seeking. People bereaved by drug overdose experience more negative health consequences than those grieving non-drug related deaths (i.e., prolonged grief disorder, substance use disorders, posttraumatic stress disorder, depression, and suicidal ideation). Overdose bereavement is common, especially among people who use drugs who may experience increases in risky substance use while grieving. Overdose deaths have a ripple effect and may increase risk for overdose morbidity and mortality among the bereaved. Peer grief support interventions hold promise for those who are grieving and may be especially important for this population because of the increased stigma, isolation, and risks this population faces. In a novel practice-research partnership, we partner with Peer Community Support Partners (PSCP) who has developed the RIVER peer grief support model for drug overdose bereavement, a promising practice that has been implemented successfully in the community, but has not yet been rigorously tested. This study seeks to not only understand whether a peer support intervention aids those grieving an overdose, but it also proactively engages and connects grievers to resources through medical examiner offices (MEOs) who contact family as part of their standard practice with death investigations. In Aim 1 (R61), through collaboration with PSCP, three MEOs, and our three advisory boards, we will adapt the RIVER training materials to our local communities, refine intervention fidelity measures, and develop intervention and MEO recruitment workflows. In Aim 2 (R61), we will conduct a pilot test with overdose bereaved participants to evaluate if we can engage participants through MEOs, measure RIVER fidelity, and evaluate if RIVER is acceptable to participants. In Aim 3 (R33), we will conduct an RCT to evaluate the effectiveness of RIVER to enhanced usual care. Participants will be recruited from MEOs and will complete baseline, 3, 6, and 12-month surveys. Post-RCT qualitative interviews will supplement data collection and will allow us to understand the characteristics that drive intervention effectiveness. We will also explore how RIVER facilitators’ well-being is affected by intervention delivery using a mixed quantitative and qualitative approach. The proposed research represents a significant step towards understanding and supporting a community that has been too long overlooked. By marrying community and research expertise, this partnership aims to build the science of overdose bereavement and provide increased support for those affected by this tragic issue. This study is part of the NIH’s Helping to End Addiction Long-term (HEAL) initiative to speed scientific solution...