Background <p>Liver transplantation (LT) is a complex procedure that results in multiple postoperative complications. Surgeons use the Clavien-Dindo classification (CDC) to evaluate the severity of complications; however, only a few studies have reported the use of the Comprehensive Complication Index^® (CCI^®) to evaluate complications associated with LT and split liver transplantation (SLT). This study explored the application of the CCI^® to evaluate complications after whole liver transplantation (WLT) and SLT.</p> Methods <p>During this retrospective study, 244 WLT and 104 SLT recipients were enrolled between January 2016 and June 2023. The clinical characteristics and postoperative complications (at hospital discharge) of the WLT and SLT groups were evaluated and compared.</p> Results <p>The median in-hospital CCI^® score was 43.9. A comparison of the WLT and SLT groups indicated no significant differences in CCI^® scores (WLT, 44.2; SLT, 43.3; <i>p</i> = 0.716). The postoperative intensive care unit stay and length of the postoperative stay were strongly correlated with the CCI^® score of the entire cohort and those of the SLT and WLT groups (all <i>p</i> &lt; 0.001). The CDC and CCI^® demonstrated a Spearman’s rank-order correlation of 0.838 (<i>p</i> &lt; 0.001). Additionally, the proportion of female recipients was significantly higher in the SLT group (25.0% vs. 16.0; <i>p</i> = 0.048). The body mass index (<i>p</i> = 0.002), Child-Pugh grade C rate (<i>p</i> = 0.017), and median model for end-stage liver disease score (<i>p</i> = 0.008) were lower in the SLT group.</p> Conclusions <p>The CCI^® is appropriate for evaluating postoperative complications of SLT and WLT.</p>