Background Mortality following major emergency abdominal surgery is high. Surgical delay is regarded as an important modifiable prognostic factor. Current care-bundles aim at reducing surgical delay, most often using a six-hour cut-off. We aimed to investigate the evidence supporting the in-hospital delay cutoffs currently used. Methods MEDLINE, EMBASE and the Cochrane Library were searched. We included studies assessing in-hospital surgical delay in major emergency abdominal surgery patients. Studies were only included if they performed adjusted analysis. Surgical delay beyond six hours was the primary cutfrom interest. The primary outcome was mortality at longest follow-up. Meta-analyses were conducted if possible. Results Eleven observational studies were included with 16,772 participants. Two studies evaluated delay in unselected major emergency abdominal surgery patients. Three studies applied a six-hour cutoff, but only a study on acute mesenteric ischemia showed an association between delay and mortality. Meta-analysis showed no association with mortality at this cutoff. An association was seen between hourly delay and mortality risk estimate, 1.02 (95% confidence interval [CI], 1.00 - 1.03), and on subgroup analysis of hourly delay in perforated peptic ulcer patients, risk estimate, 1.02 (95% CI, 1.0 - 1.03). All risk estimates had a very low Grading of Recommendations Assessment, Development, and Evaluation score. Conclusion Little evidence supports a six-hour cutoff in unselected major emergency abdominal surgical patients. We found an association between hourly delay and increased mortality; however, evidence supporting this was primarily in patients undergoing surgery for perforated peptic ulcer. This review is limited by the quality of the individual studies.