Abstract: The aim of this study, was to determine the effects of dexamethasone on sperm characteristics (volume, mass motility, individual motility, sperm concentration, osmotic pressure) and testosterone activity of serum. In this study, 9 healthy Awassi rams, at the age of 3-5 years and weighing between 50-60 kg, were used. The rams were randomly divided into 2 groups (4 in control group and 5 in treatment group). Dexamethasone was administered intramuscularly at a dose of 4 mg ram 1 once weekly for 3 weeks, semen samples were collected from the rams 2, 24 and 48 h after each injection weekly and examined for sperm characteristics. The results showed that the use of dexamethasone caused significant (p<0.05) increase in semen volume, mass motility and individual sperm motility as compared to the control group. There was no significant correlation (p<0.05) in semen osmotic pressure and sperm concentration. Blood samples were collected from the ram before treatment, after 10 and 25 days of treatment and examined for serum testosterone. The result showed there are significant difference (p<0.05) after 25 days after treatment when compared with the control group.