Background: Emergency groin hernia repair is associated with increased mortality risk, but the actual risk is unknown. Therefore, this review aimed to investigate 30- and 90-day postoperative mortality in adult patients who had undergone emergency or elective groin hernia repair. Methods: This review was reported following PRISMA 2020 guidelines, and a protocol (CRD42021244412) was registered to PROSPERO. A systematic search was conducted in PubMed, EMBASE, and Cochrane CENTRAL in April 2021. Studies were included if they reported 30- or 90-day mortality following an emergency or elective groin hernia repair. Meta-analyses were conducted when possible, and subgroup analyses were made for bowel resection, sex, and hernia type. According to the study design, the risk of bias was assessed using either the Newcastle–Ottawa Scale or Cochrane Risk of Bias tool. Results: Thirty-seven studies with 30,740 patients receiving emergency repair and 457,253 receiving elective repair were included. The 30-day mortality ranged from 0–11.8% to 0–1.7% following emergency and elective repair, respectively. The risk of 30-day mortality following emergency repair was estimated to be 26-fold higher than after elective repair (RR = 26.0, 95% CI 21.6–31.4, I² = 0%). A subgroup meta-analysis on bowel resection in emergency repair estimated 30-day mortality to be 7.9% (95% CI 6.5–9.3%, I² = 6.4%). Subgroup analyses on sex and hernia type showed no differences regarding the mortality risk in elective surgery. However, femoral hernia and female sex significantly increased the risk of mortality in emergency surgery, both given by a risk ratio of 1.7. Conclusion: The overall mortality after emergency groin hernia repair is 26-fold higher than after elective repair, but the increased risk is attributable mostly to female and femoral hernias. Trial registration: PROSPERO protocol (CRD42021244412). Graphical abstract: [Figure not available: see fulltext.]