Background: Perioperative shivering is a common complication in modern anesthesia. It's usually defined as readily detectable fasciculation or tremors of the face, jaw, head, trunk or extremities lasting longer than 15 seconds. Aim of the work: Compare the anti-shivering effect of parentral low dose ketamine and ondansetron after spinal anesthesia during hernia surgery, as well as the anticipated side effects and complications. Patients and Methods: This study presents a prospective randomized single blinded study. After obtaining approval from the medical ethical committee of Ain Shams University, this study was conducted in Ain Shams University hospitals operating rooms. Study period was from January 2018 to May 2018. Results: Our results indicated that low dose ketamine and ondansetron were effective, with more extent to ketamine, in prevention of post spinal shivering in patients undergoing hernia surgery and these results agreed with other results of studies done before. Conclusion: Our results indicated that Prophylactic low dose ketamine (0.25mg/kg) and Ondansetron (4mg) significantly decreased shivering in patients undergoing spinal anesthesia without significant side effects. Ketamine found to be more effective in controlling post spinal shivering.