Background: Dexamethasone is a common medicine used for treatment of sever allergies in human and able to induce disturbance in male reproductive system by inducing oxidative stress. Pentoxiphylin as a potent antioxidant is able to reduce oxidative stress. The aim of this study was to evaluate the preventing effect of pentoxiphylin on undesirable morphological changes in mice testis tissue treated with dexamethasone. Material and Method: 24 Adult male NMRI mice (36±2 gr.) were divide randomly into 4 groups (n=6): control, Dexamethasone (7mg/kg/day), Dexamethasone + pentoxiphylin (200mg/kg/day) and pentoxiphylin. After 7 days of intraperitoneal injection, testes weighted and fixed for stereological evaluation of testis morphological changes, daily sperm production and spermatogenesis indexes. Data was statistically analyzed using one-way ANOVA and tukey’s test, and the means were consider significant different at P<0/05. Results: A significant reduction in the mean total volume of testis, volume of seminiferous tubules, mean number of spermatocytes, round and long spermatids and Leydig cells, spermatogenesis indexes, daily sperm production was found in the Dexamethasone group compared to the control group (P>0/05(. The mentioned parameters were compensated to the control level in the Dexamethasone + pentoxiphylin group. Conclusion: This study showed that simultaneous treatment of pentoxiphylin and dexamethasone can prevent the adverse effects of dexamethasone on mice testicular histological changes, spermatogenesis indexes. Therefore its application in the therapeutic regimens including Dexamethasone is suggested.