Background Consistent evidence has demonstrated stark inequities in postoperative mortality for indigenous Māori patients in Aotearoa New Zealand. This may be contributed to by higher rates of complications, or higher rates of ‘failure to rescue’ (FTR) from complications. Methods All patients undergoing gastrointestinal or hepatopancreatobiliary cancer resection in Aotearoa from 2005-2020 were identified. FTR was defined as the mortality rate for patients with any of 19 complications. Age-standardised and risk-adjusted rates of 90-day mortality, complications, and FTR were calculated. Temporal trends in risk-adjusted outcomes for Māori and Pakeha were compared. Results In total, 31,185 patients with available ethnicity data were included. Māori (8%) and Pacifica (3%) were under-represented compared to the Aotearoa population. Māori had higher age-standardised mortality (5.9%) and FTR (10.8%) compared to Pakeha (mortality 3.2%, FTR 7.2%). After adjustment for demographic, oncological, surgical, and hospital factors, Māori had a higher risk of mortality (OR 1.4, 95% CI 1.2-1.8), complications (OR 1.3, 95% CI 1.2-1.5) and FTR (OR 1.3, 95% CI 1.0-1.6). Analysis of changes over time demonstrated a large improvement in risk-adjusted mortality for Pakeha (6.1 to 3.5%), driven by improvements in FTR (7.3 to 4.0%). However, no significant improvement in mortality (6.6 to 5.4%) or FTR (7.8 to 6.4%) over time was observed for Māori. Conclusion Inequities in postoperative mortality for Māori are contributed to by higher rates of both postoperative complications and FTR. Improvements in mortality and FTR for Pakeha have not been experienced by Māori. Urgent action is needed to address these inequities in perioperative care in Aotearoa.