Background: Previous before-and-after studies indicate that the use of safety checklists in surgery reduces complication rates in patients. Methods: A systematic review of studies was undertaken using MEDLINE, CINAHL, Proquest, and the Cochrane Library to identify studies that evaluated the effects of checklist use in surgery on complication rates. Study quality was assessed using the Methodological Index for Nonrandomized Studies. The pooled risk ratio (RR) was estimated using both fixed and random effects models. For each outcome, the number needed to treat (NNT) and the absolute risk reduction (ARR) were also computed. Results: Of the 207 intervention studies identified, 7 representing 37,339 patients were included in meta-analyses, and all were cohort studies. Results indicated that the use of checklists in surgery compared with standard practice led to a reduction in any complication (RR, 0.63; 95% CI, 0.58 to 0.72; P < 0.0001; ARR, 3.7%; NNT, 27) and wound infection (RR, 0.54; 95% CI, 0.40 to 0.72; P = 0.0001; ARR, 2.9%; NNT, 34) and also reduction in blood loss (RR, 0.56; 95% CI, 0.45 to 0.70; P = 0.0001; ARR, 3.8%; NNT, 33). There were no significant reductions in mortality (RR, 0.79; 95% CI, 0.57 to 1.11; P = 0.191; ARR, 0.44%; NNT, 229), pneumonia (RR, 1.03; 95% CI, 0.73 to 1.4; P = 0.857; ARR, 0.04%; NNT, 2,512), or unplanned return to operating room (RR, 0.75; 95% CI, 0.56 to 1.02; P = 0.068; ARR, 0.52%; NNT, 192). Conclusion: Notwithstanding the lack of randomized controlled trials, synthesis of the existing body of evidence suggests a relationship between checklist use in surgery and fewer postoperative complications.