Background: Formerly incarcerated people have exceptionally poor health profiles and are at increased risk of adverse health outcomes when compared to their general population peers. However, not enough is currently known about the epidemiology of preventable mortality in this population to inform the development of targeted, evidence-informed responses. Methods: We analyzed mortality data relating to 1,471526 people released from incarceration in eight countries from 1980-2018, across 10,534441 person-years of follow-up time (range: 0-24 years). We used individual participant data meta-analysis to estimate pooled all-cause and cause-specific crude mortality rates (CMRs) with 95% confidence intervals (95%CI) for specific time periods after release, overall and stratified by age, sex, and region. Results: 75427 deaths were recorded. The all-cause mortality rate was highest during days 2-7 following release, with the highest cause-specific rates during this period due to alcohol and other drug poisoning (CMR: 657; 95%CI: 332-1,076), suicide (CMR: 135; 95%CI: 36-277), and cardiovascular disease (CMR: 71; 95%CI: 16-153). We observed considerable variation in cause-specific CMRs over time and across regions, yet little difference in pooled all-cause CMRs between males (731; 95%CI: 630-839) and females (660; 95%CI: 560-767). Pooled all-cause CMRs were higher in older age groups. Conclusions: The markedly elevated rate of death in the first week post-release underscores an urgent need for coordinated transitional healthcare, including pre-release treatment for mental and substance use disorders to prevent post-release deaths suicide and overdose deaths. Variations in causes of death according to time since release highlights the need for routine monitoring of post-release mortality.