BACKGROUND The aim of this study was to determine the clinical benefit of transhepatic arterial chemoembolization (TACE) with or without recombinant human adenovirus type 5 (H101) administration for the treatment of patients with hepatocellular carcinoma (HCC). METHODS Tumor response, progression-free survival (PFS), and overall survival(OS) were retrospectively evaluated in consecutive patients with unresectable HCC who received TACE with or without H101 between April 2012 and April 2013. RESULTS Patients with unresectable HCC were treated with transarterial injection of H101 with TACE (H101 group, n = 87) or TACE alone (control group, n = 88). Clinicopathological features were similar between the groups. Treatment response was significantly different between the groups (P = 0.01). In the H101 group, 25 patients demonstrated a complete response (CR, 28.7 %); 28 patients, a partial response (PR, 32.2 %); 23 patients, stable disease (SD, 26.4 %); and 11 patients, progressive disease (PD, 12.6 %). In the control group, 13 patients demonstrated CR (14.8 %); 19, PR (21.6 %); 34, SD (38.6 %); and 22, PD (25 %). OS and PFS was also significantly different between the groups. In the H101 group, median OS and PFS were 12.8 and 10.49 months, whereas in the control group they were 11.6 and 9.72 months, respectively (OS: P = 0.046; PFS: P = 0.044). CONCLUSIONS In patients with unresectable HCC, H101 combined with TACE improves OS, PFS and treatment response compared with TACE alone.