Background: postoperative shivering is a common complication of various surgical, so far no acceptable theory has been presented on the prevention of it. The aim of this study was to compare the effect of intravenous injection of dexmedetomidine, ondansetron, and pethidine on postoperative shivering among patients under abdominal surgery. Materials and Methods: In a double-blind clinical trial study, 128 patients undergoing abdominal surgery were selected and randomly divided into four groups of 32. In the 4 groups, 0.5 μg/kg dexmedetomidine, 0.5 mg/kg pethidine, 0.1 mg/kg ondansetron, and the same volume of normal saline were injected intravenously when anesthetics were discontinued and the incidence and severity of postoperative shivering were determined and compared in four groups. Results: The incidence of postoperative shivering was 12.5% in the dexmedetomidine group, 31.3% in the ondansetron group, 31.3% in the pethidine group, and 50% in the control group (P = 0.015). The mean of shivering severity in the four groups was 1.33 ± 0.5, 0.17 ± 0.8, 1.09 ± 0.4, and 1.13 ± 0.39, and the difference between the four groups was significant (P = 0.005). Conclusion: The use of all three drugs of dexmedetomidine, ondansetron, and pethidine is effective in decreasing the incidence of postoperative shivering, but the use of dexmedetomidine is associated with less postoperative shivering, better hemodynamic stability, and fewer other postoperative complications.