Hepatocellular carcinoma (HCC) remains one of the most lethal malignancies. The current chemotherapy with typically low tumor uptake and high toxicity reveals a poor anti-HCC efficacy. Here, we report transferrin-guided polycarbonate-based polymersomal doxorubicin (Tf-Ps-Dox) as a low-toxic and potent nanotherapeutic agent for effective treatment of liver tumor using a transferrin receptor (TfR)-positive human liver tumor SMMC-7721 model. Tf-Ps-Dox was facilely fabricated with small size of ca. 75 nm and varying Tf densities from 2.2% to 7.0%, by postmodification of maleimide-functionalized Ps-Dox (Dox loading content of 10.6 wt%) with thiolated transferrin. MTT assays showed that Tf-Ps-Dox had an optimal Tf surface density of 3.9%. The cellular uptake, intracellular Dox level, and anticancer efficacy of Tf-Ps-Dox to SMMC-7721 cells were inhibited by supplementing free transferrin, which supports that Tf-Ps-Dox is endocytosed through TfR. Interestingly, Tf-Ps-Dox exhibited a high accumulation of 8.5%ID/g (percent injected dose per gram of tissue) in subcutaneous SMMC-7721 tumors, which was 2- and 3-fold higher than that of nontargeted Ps-Dox and clinically used liposomal Dox formulation (Lipo-Dox), respectively. The median survival times of mice bearing orthotopic SMMC-7721 tumors increased from 82, 88 to 96 days when treated with Tf-Ps-Dox at Dox doses from 8, 12 to 16 mg/kg, which was significantly longer than that of Ps-Dox at 8 mg/kg (58 days) and Lipo-Dox at 4 mg/kg (48 days) or PBS (36 days). Notably, unlike Lipo-Dox, no body weight loss and damage to major organs could be discerned for all Tf-Ps-Dox groups, indicating that Tf-Ps-Dox caused low systemic toxicity. This transferrin-dressed polymersomal doxorubicin provides a potent and low-toxic treatment modality for human hepatocellular carcinoma. STATEMENT OF SIGNIFICANCE: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. Vast work has focused on developing HCC-targeted nanotherapeutics. However, none of the nanotherapeutics has advanced to clinics, partly because the ligands used have not been validated in patients. Transferrin (Tf) is a natural ligand for transferrin receptor (TfR) that is overexpressed on cancerous cells, and it is currently under clinical trials (MBP-426 and CALAA-01) for the treatment of solid tumors. We designed Tf-functionalized polymersomal doxorubicin (Tf-Ps-Dox) for targeted therapy of orthotopic SMMC-7721 tumor in nude mice. Tf-Ps-Dox showed potent anti-HCC efficacy and significantly improved survival time with low toxicity as compared with nontargeted Ps-Dox and clinical liposomal Dox (Lipo-Dox). Hence, Tf-Ps-Dox is very appealing for targeted treatment of HCC.