Background and Objectives: Several drugs and methods are used to reduce postoperative shivering, the most common complications occurring after surgery. This study aimed to evaluate the effects of the oral Clonidine and Tramadol premedication in reducing postoperative shivering after spinal anesthesia. Materials and Methods: In this study, patients aged 20 -60 years, based on the American Society of Anesthesia functional class I (Anesthesiologists grade-1), were included in controlled double-blind clinical trials. Each was a candidate of a hydrocele, varicocele, and inguinal hernia under spinal anesthesia. The patients were assigned to three groups and 1 h prior to surgery, group A received 0.2 mg of Clonidine, group B received 50 mg of a Tramadol tablet, and group C received a placebo. We collected information on the severity of shivering, pain intensity levels (VAS score), duration of analgesia, and the patients' hemodynamic condition at base time of 5, 15, and 30 min and 1, 2, 4, and 6 h postoperatively. Results: The incidence of shivering was significantly lower in the Clonidine group than that in the other groups. Analgesia duration was significantly longer in the Clonidine group than that in the control group. In this study, side effects in different groups were not significantly different from each other. Conclusion: Results of this study showed that the oral administration of Clonidine can be effective in preventing the side effects and shivering after spinal anesthesia.