Polydeoxyribonucleotide (PDRN) is an agonist of the A2A adenosine receptors. We evaluated the effects of PDRN on liver regeneration induced by partial hepatectomy (PH) in rats, focusing on cell proliferation. Proliferating cell nuclear antigen (PCNA) as an indicator of cell proliferation was targeted to determine whether PDRN treatment could promote proliferation of hepatic cells in regenerating liver. Male Sprague-Dawley rats were divided into three groups: normal group (n = 3) without PH (sham operated), control groups (n = 12) with saline injection after PH, and experimental groups (n = 12) with i.p. injection of 8 mg/kg of PDRN immediately after PH. Light microscopically, liver regeneration induced by PH involved proliferation of various hepatic cells including parenchymal cells and Kupffer cells. The disintegration (1 or 2 days after PH) and remodeling (4 days after PH) of hepatic plate and increase of sinusoids (6 days after PH) were sequentially observed. These regenerative processes occurred relatively earlier in the experimental groups. By western blotting, the expression of PCNA increased in the early stage, reached its peak at 1 and 2 days after PH, and decreased thereafter. By immunohistochemistry, the intensities of PCNA staining in the experimental groups were more obvious at various days after PH. By electron microscopy using immunogold labeling for PCNA, the gold particles were largely observed in heterochromatin and nucleolus in hepatic cells. The results of immunochemistry and western blotting for PCNA showed the similar pattern in most groups. These findings suggest that PDRN treatment to hepatectomized rat could accelerate liver regeneration through rapid cell proliferation.