Objective: To investigate the incidence of systemic inflammatory response syndrome (SIRS) on emergency department admission and the prognostic significance of SIRS in patients undergoing emergency surgery. Methods: This is a retrospective study of 889 adults who were admitted as emergency cases and were operated on within 24 hours of admission. Data on patient demography, clinical information including comorbidities, categories of surgery, American Society of Anesthesiologists physical status, SIRS score, postoperative outcomes including duration of mechanical ventilation, intensive care unit (ICU) and hospital lengths of stay, and mortality were collected. Results: SIRS occurred in 43% of the patients and was associated with a significantly worse outcome in terms of duration of ventilator use (10.5 ± 15.4 vs. 3.5 ± 4.4 days, p < 0.001), ICU stay (11.2 ± 13.6 vs. 5.0 ± 5.4 days, p < 0.001), hospital length of stay (19.4 ± 22.4 vs. 7.1 ± 7.6 days, p < 0.001) and mortality (12.7% vs. 0.4%, p < 0.001). After adjusting for covariates (including age, gender, American Society of Anesthesiologists physical status, comorbid conditions, and surgery categories), SIRS was independently associated with higher mortality (adjusted odd ratio, 21.5; 95% confidence interval (CI), 4.9–93.2), longer ventilator duration (adjusted coefficient, 7.8; 95% CI, 3.2–12.5), longer ICU stay (adjusted coefficient, 6.2; 95% CI, 2.6–9.8) and longer hospital stay (adjusted coefficient, 9.7; 95% CI, 7.5–11.9). Conclusion: The presence of SIRS at admission in patients receiving emergency surgery predicted worse outcomes and higher mortality rates.