Acute liver failure (ALF) is a life-threatening condition with devastating complications and high mortality. This study was planned to evaluate the effect of endogenous hematopoietic stem cell (HSC) mobilization, by granulocyte-colony stimulating factor (G-CSF) “Neupogen”, in promoting liver regeneration and recovery from thioacetamide (TAA)-induced ALF in rats. This study was carried out on 48 adult female albino rats that were divided into control group, and experimental group which received a single intraperitoneal injection of TAA at a dose of 300 mg/kg. Rats of this group were subdivided equally into: (1) Group II (non-treated group). (2) Group III (G-CSF-treated group) that received G-CSF “Neupogen” subcutaneously at a dose of 50µg/kg/day and then daily for a total of 5 consecutive days. Animals were sacrificed after 1, 3, 5 and 9 days from the beginning of the experiment. Liver specimens were processed for Hematoxylin and Eosin, Masson’s trichrome and immunohistochemical staining for CD34 and Ki-67. Serum alanine aminotransferase (ALT) level was also measured. As compared to the non-treated group, the treated group exhibited significant reduction in ALT level, improved histological architecture with less hepatic injury, and increased number of CD34 positive HSCs and Ki-67 positive hepatocytes in the liver sections. This reflects the beneficial effect of G-CSF “Neupogen” in treating ALF.