This study aimed to investigate the pathological changes occurring in lungs and liver of male mice exposed to different doses of Benzo[a]pyrene (B[a]P) over varying durations. B[a]P is a potent carcinogenic polycyclic aromatic hydrocarbon commonly found in the environment, primarily adsorbed to particulate matter. Ninety mature mice were divided into three groups: a control negative group, a group injected with a single dose of 50 mg/kg bw of B[a] P, and a group injected with a single dose of 100 mg/kg bw of B[a] P. The experiment was conducted over several months, with ten mice from each group being sacrificed at 3, 6, and 9 months. Serum samples were collected for biochemical tests to assess liver function and tumor marker alpha-fetoprotein levels. Additionally, postmortem examinations were performed; lung and liver tissue specimens were collected for histopathological analysis. The results of the biochemical tests revealed a significant increase in Alanine aminotransferase (ALT), Aspartate aminotransferase (AST) and alpha-fetoprotein levels. Histopathological examination of the lung tissues showed a gradual initiation of mild hyperplastic proliferation in the bronchiolar epithelia at both half (50 mg/kg bw) and full (100 mg/kg bw) doses of B[a] P, with more pronounced changes observed in the full-dose groups at 6 and 9 months. At 9 months of full-dose treatment, a well-defined circumscribed tumor mass was detected. In the liver, cellular changes were observed at 3 months for both half and full doses of B[a]P, progressing to malignant changes at 6 months and ultimately leading to the development of hepatocellular adenocarcinoma at 9 months.