Background: The aim of this study was to compare the effectiveness of saline versus metronidazole peritoneal lavage in patients undergoing surgery for peritonitis.Materials and Methods: This longitudinal study involved 130 patients with peritonitis who underwent surgical intervention at a tertiary care hospital. Patients were randomly assigned to two groups: saline lavage (65 patients) and metronidazole lavage (65 patients). Demographic data, cause of peritonitis, postoperative infection rates, length of hospital stay, fever resolution time, mortality, and complications were assessed. The primary outcome measure was the incidence of postoperative infections.Results: There were no significant differences between the two groups in terms of demographic characteristics, infection rates, length of hospital stay, time to fever resolution, or mortality. The saline group had a slightly higher rate of postoperative infections (12.31%) compared to the metronidazole group (7.69%), but this difference was not statistically significant (p-value 0.346). Both groups had low mortality rates (3.08% in the saline group and 1.54% in the metronidazole group, p-value 0.578), and complications were minimal.Conclusion: This study concluded that there were no significant differences between saline and metronidazole peritoneal lavage in patients undergoing surgery for peritonitis. Both lavage methods demonstrated similar outcomes, suggesting that the type of lavage solution does not significantly affect clinical outcomes in peritonitis management.