Background: Studies show that gasoline inhalation has severe damage on certain tissues in body. This study aimed to determine the effects of gasoline vapor inhalation on serum testosterone level and testes tissue in male rats. Methods: Male Wistar rats were randomly divided into control and experimental groups exposed to gasoline vapor for 1, 2 or 3 h/day of 5 rats in each group. After 12 weeks, blood samples were collected using the cardiac puncture method. Serum testosterone was measured using the radioimmunoassay method. Testes tissue was examined histologically using Hematoxylin and Eosin staining method. Data were analyzed using one way-ANOVA. Results: Serum testosterone level significantly increased in rats exposed to gasoline vapor for 1, 2, 3 hours/day compared with control group. The number of spermatogonia cells significantly decreased in experimental groups compared to control rats; However, the number of spermatocytes and Sertoli cells, and the seminiferous tunnel diameter did not significantly change in groups exposed to gasoline vapor compared with control rats. Conclusion: Inhalation of gasoline vapor had deleterious effects on testis tissue, resulting in decreased number of spermatogonia cells and increased serum testosterone level.