BACKGROUND & AIMS: Treatment with immune checkpoint inhibitors (ICIs) for hepatocellular carcinoma (HCC) prior to liver transplantation (LT) has been reported; however, ICIs may elevate the risk of allograft rejection and impact other clinical outcomes. This study aims to summarize the impact of ICI use on post-LT outcomes. METHODS: In this individual patient data meta-analysis, we searched databases to identify HCC cases treated with ICIs before LT, detailing allograft rejection, HCC recurrence, and overall survival. We performed Cox regression analysis to identify risk factors for allograft rejection. RESULTS: Among 91 eligible patients, with a median (IQR) follow-up of 690.0 (654.5) days, there were 24 (26.4%) allograft rejections, 9 (9.9%) HCC recurrences, and 9 (9.9%) deaths. Age (adjusted hazard ratio [aHR] per 10 years 0.72, 95% CI 0.53-0.99, p = 0.044) and ICI washout time (aHR per 1 week 0.92, 95% CI 0.86-0.99, p = 0.022) were associated with allograft rejection. The median (IQR) washout period for patients with ≤20% probability of allograft rejection was 94 (196) days. Overall survival did not differ between cases with and without allograft rejection (log-rank test, p = 0.2). Individuals with HCC recurrence had fewer median (IQR) ICI cycles than those without recurrence (4.0 [1.8] vs. 8.0 [9.0]; p = 0.025). The proportion of patients within Milan post-ICI was lower for those with recurrence vs. without (16.7% vs. 65.3%, p = 0.032). CONCLUSION: Patients have acceptable post-LT outcomes after ICI therapy. Age and ICI washout length relate to the allograft rejection risk, and a 3-month washout may reduce it to that of patients without ICI exposure. Number of ICI cycles and tumor burden may affect recurrence risk. Large prospective studies are necessary to confirm these associations. IMPACT AND IMPLICATIONS: This systematic review and individual patient data meta-analysis of 91 patients with hepatocellular carcinoma and immune checkpoint inhibitor use prior to liver transplantation suggest acceptable overall post-transplant outcomes. Older age and longer immune checkpoint inhibitor washout period have a significant inverse association with the risk of allograft rejection. A 3-month washout may reduce it to that of patients without immune checkpoint inhibitor exposure. Additionally, a higher number of immune checkpoint inhibitor cycles and tumor burden within Milan criteria at the completion of immunotherapy may predict a decreased risk of hepatocellular carcinoma recurrence, but this observation requires further validation in larger prospective studies.