Objective Nowadays, conventional analgesic agents, which are widely used for pain relief after cesarean section, provide suboptimal analgesia with occasional serious side effects. We designed a randomized, double-blind, placebo-controlled study to evaluate the analgesic efficacy of intrathecal ketamine added to bupivacaine after cesarean section. Methods Sixty patients scheduled for cesarean section under spinal anesthesia were randomly allocated to one of the two groups to receive either bupivacaine 10 mg combined with 0.1 mg/kg ketamine, or bupivacaine 10 mg combined with 0.5 mL distilled water intrathecally. The time to the first analgesic request, analgesic requirement in the first 24 hours after surgery, onset times of sensory and motor blockades, the durations of sensory and motor blockades, and the incidences of adverse effects such as hypotension, ephedrine requirement, bradycardia, and hypoxemia, were recorded. Results Patients who received ketami...