Background A prior in vitro study showed that idarubicin was the most cytotoxic agent for hepatocellular carcinoma (HCC) cell lines. Idarubicin-loaded beads for transarterial chemoembolization (TACE) were previously evaluated for the appropriate dose in a phase I dose-escalation study. Purpose To evaluate objective response rate (ORR), safety, and survival after TACE by using idarubicin-loaded beads for unresectable HCC. Materials and Methods This prospective single-arm phase II study was conducted between January 2015 and January 2017. Participants with unresectable HCC were included in the trial and underwent TACE with idarubicin-eluting beads. The primary end point was 6-month ORR assessed with independent central review by using modified Response Evaluation Criteria in Solid Tumors. Secondary end points were best ORR during the first 6 months, overall survival, progression-free survival, time to progression, and safety. A two-stage Fleming statistical design was used. Results Forty-six study participants (mean age, 71.2 years ± 10.2; six women and 40 men) were included; 44 participants underwent at least one TACE session. The 6-month ORR was 52% (23 of 44). The best ORR achieved was 68% (30 of 44). Fourteen of 44 (32%) participants underwent a curative treatment after TACE. Median progression-free survival, time to progression, and overall survival were 6.6 months, 9.5 months, and 18.6 months, respectively. TACE was discontinued for toxicity in four of 44 (9%) participants. The most frequent grade 3-4 adverse events were elevated aspartate aminotransferase (14 of 44, 32%), elevated γ-glutamyl transpeptidase (eight of 44, 18%), hyperbilirubinemia (seven of 44, 16%), elevated alanine aminotransferase (seven of 44, 16%), and pain (seven of 44, 16%). Conclusion Idarubicin-eluting beads showed a good safety profile and promising objective response rate and time to progression when used as part of a transarterial chemoembolization regimen for unresectable hepatocellular carcinoma. © RSNA, 2019 See also the editorial by Padia in this issue.