Cardiovascular complications after major surgery are associated with increases in morbidity and mortality. There is confusion over definitions of cardiac injury or complications, and variability in the assessment and management of patients. This international prospective cohort study aimed to define the incidence and timing of these complications and to investigate their impact on 30-day all-cause mortality. We performed a prospective, international cohort study between January 2022 and May 2022. Data were collected on consecutive patients undergoing major abdominal surgery in 446 hospitals from 28 countries across Europe. The primary outcome measure was cardiovascular complications as defined by the Standardised Endpoints for Perioperative Medicine-Core Outcome Measures for Perioperative and Anaesthetic Care initiative up to 30 days after surgery. The secondary outcome was 30-day postoperative mortality. This study included 24,203 patients, of whom 611 (2.5%) developed cardiovascular complications. In total, 458 (1.9%) patients died within 30 days of surgery, of which 123 (26.9%) deaths were judged to be cardiac-related. Mortality rates were higher in patients who developed postoperative cardiovascular complications than in those who did not (19.8% vs. 1.4%), which persisted after risk adjustment (hazard ratio (95%CI) 4.15 (3.14–5.48)). We estimated an absolute risk reduction (95%CI) of 0.4 (0.3–0.5) in mortality in the absence of all cardiovascular complications. This would confer a relative risk reduction in mortality of 21.1% if all cardiovascular complications were prevented. Postoperative cardiovascular complications are relatively common and occur early after major abdominal surgery. However, over 1 in 5 postoperative deaths were attributable to these complications, highlighting an important area for future randomised trials.