This study aimed to investigate the efficacy of avocado oil against diethylnitrosamine (DEN) – induced hepatocarcinogenesis in rats. Rats were divided into 5 groups. Group (1) was negative control. Groups (2) and (4) were orally administrated diethylnitrosamine for induction of hepatocellular carcinoma then group (2) was left untreated; group 4 was treated orally with avocado oil before DEN administration. Group (3) was orally treated with avocado oil only. Serum alpha-fetoprotein (AFP) was assayed using ELISA technique. The untreated cancer group showed significant elevation in the liver function (ALT, AST, ALP, total bilirubin and direct bilirubin) and tumor marker AFP. Histopathological investigation of liver tissue sections in cancer group revealed dysplasia. In contrast, the treated groups showed significant depletion in the liver function and AFP and significant decrease in the liver function (ALT, AST, ALP, total bilirubin and direct bilirubin). Interestingly, treatment with avocado oil showed marked improvement in the histological feature of liver tissue. It is concluded that this study indicated the promising therapeutic potential of avocado oil against DEN-induced hepatocarcinogenesis. Further studies are required to evaluate the possible mechanism at the molecular level.