The Zataria multiflora Boiss is endemic plant of Iran, Pakistan and Afghanistan. Several traditional purposes have been indicated for this medicinal plant including medical purposes, natural preservative of a wide variety of foods and as a food flavour. Currently, the correlation has been found between the essential oil of Z. multiflora Boiss and anti-carcinogenesis effects by regulation of two controller genes of mammalian cell cycle named ATM and MDM2. The aim of this study is to understand the molecular response of retinoblastoma tumor suppressor gene (Rb1) and protein (pRb) to the essential oil of this plant. Rb1 gene is required for inhibiting of cell cycle entering to S-phase and its inactivation contributes to tumorigenesis. In present study, liver samples of eight normal male rats were examined for expression analysis of retinoblastoma tumor suppressor gene and its product by using Semi-quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and western blotting methods, respectively. The statistical analysis was conducted using SPSS software through independent-sample T-test. The essential oil supplementation at concentration of 50 µl/kg body weight per day induced significantly upregulation in gene and protein expression of Rb1 tumor suppressor in rat liver after one week treatment (P = 0.001). Induction in level of retinoblastoma tumor suppressor by essential oil of Z. multiflora Boiss along with its property in regulation of ATM and MDM2 genes expression appear to play an important role in cell cycle control. This data implicated that the essential oil of Z. multiflora Boiss may offer new tools for therapeutic intervention in the retinoblastoma pathway for cancer prevention and treatment. This is the first report showing the potential role of essential oil of Z. multiflora Boiss as a new class of natural retinoblastoma tumor suppressor inducer and therefore, it could be used as a natural preservative ingredient in food and pharmaceutical industries. Key words: Zataria multiflora Boiss, retinoblastoma tumor suppressor, essential oil, cancer.