Objectives. To compare the outcomes of extended postoperative antibiotics versus no postoperative antibiotics in patients with acute calculous cholecystitis undergoing emergency cholecystectomy. Methods. We performed a systematic review and conducted a search of electronic information sources to identify all randomized controlled trials comparing outcomes of extended postoperative antibiotics versus no postoperative antibiotics in patients with acute calculous cholecystitis undergoing emergency cholecystectomy. Postoperative infectious complications and surgical site infections were primary outcome measures. The secondary outcome measures included postoperative morbidity, postoperative noninfectious complications, urinary tract infections, pneumonia, length of hospital stay, postoperative mortality, and need for readmission. Random or fixed effects modeling was applied to calculate pooled outcome data. Results. Four randomized controlled trials enrolling 953 patients were identified. The included populations in the extended antibiotic group and no antibiotic group were comparable in terms of baseline characteristics. There was no difference between the 2 groups in terms of postoperative infectious complications (odds ratio [OR] =0.94, P = .79), surgical site infections (OR = 1.13, P = .72), postoperative morbidity (OR = 0.93, P = .70), postoperative noninfectious complications (OR = 0.85, P = .57), urinary tract infections (OR = 0.69, P = .55), pneumonia (OR = 0.33, P = .14), length of hospital stay (mean difference = 0.78, P = .25), postoperative mortality (risk difference = −0.00, P = .65), and need for readmission (OR = 0.87, P = .70). Conclusions. Our results suggest that extended postoperative antibiotic therapy does not improve postoperative infectious or noninfectious outcomes in patients with mild or moderate acute calculous cholecystitis undergoing emergency cholecystectomy. Postoperative antibiotics should not be routinely used and should be preserved only for selected cases.