Background: Nausea and vomiting, after pain, is the most common adverse effect of cesarean section, such that it is reported in more than 66% of the patients undergoing cesarean section delivery under spinal anesthesia. There are several treatment choices for this problem, including injection of metoclopramide and ondansetron. This study aimed to compare the antiemetic efficacy of these two medications. Methods: This double-blind, interventional study was conducted on 120 women undergoing cesarean section at Amir-Al Momenin Hospital, Zabol, Iran. The patients were randomly assigned to metoclopramide (10 mg) and ondansetron (4 mg) groups. The rate of nausea and vomiting was assessed in both groups immediately after cesarean section and every 6 h until 24 h after the operation. To analyze the data, Chi-squared test, McNemar's test, paired t-test, and Wilcoxon signed-rank test were run, using SPSS version 21 software. Results: In total, the mean age of the participants was 30.41 ± 8.22 y. The frequency rates of nausea and vomiting in the ondansetron group at 0, 6, 12, and 24 hours after the operation were 36.7%, 35.0%, 16.7%, 3.3% respectively. The corresponding figures for metoclopramide group were 28.3%, 21.7%, 18.3%, and 10.0% respectively. Conclusion: Our study showed that ondansetron does not have any superiority to metoclopramide in terms of reducing post-cesarean nausea/vomiting. To confirm our results, further longitudinal studies with larger sample sizes are recommended.