Background Emergency laparotomy (EL) is a common urgent surgical procedure with high risk for postoperative complications. Complications impair the prognosis and prolong the hospital stay. This study explored the incidence and distribution of complications and their impact on short-term mortality after EL. Methods This was a retrospective single-center register-based cohort study of 674 adults undergoing midline EL between May 2015 and December 2017. The primary outcome was operation-related or medical complication after EL. The secondary outcome was mortality in 90-day follow-up. Multivariate logistic regression analyses were used to identify independent risk factors for complications. Results A total of 389 (58%) patients developed complications after EL, including 215 (32%) patients with operation-related complications and 361 (54%) patients with medical complications. Most of the complications were Clavien-Dindo classification type 4b (28%) and type 2 (22%). Operation-related complications occurred later compared to medical complications. Respiratory complications were the most common medical complications, and infections were the most common operation-related complications. The 30- and 90-day mortalities were higher in both the medical (17.2%, 26.2%) and operation-related complication groups (13.5%, 24.2%) compared to patients without complications (10.5% and 4.8%, 14.8% and 8.0%). Low albumin, high surgical urgency, excessive alcohol consumption and medical complications were associated with operation-related complications. Older age, high ASA class and operation-related complications were associated with medical complications. Conclusions This study demonstrated that EL is associated with a high risk of complications and poor short-term outcome. Complications impair the prognosis regardless of which kind of EL is in question.