Introduction: Liver resection is the primary modality with curative intent for liver malignancy. The National Surgical Quality Improvement Program (NSQIP) by the American College of Surgeons (ACS) is a surgical risk calculator designed to predict 30-day post-operative outcomes based on the patient’s clinical factors. However, the performance of this tool in liver resection for a primary malignancy within an Australian context has not been evaluated. This study aimed to assess the performance of the ACS-NSQIP surgical risk calculator in patients undergoing liver resection for primary liver malignancy. Methods: A retrospective review of patients who underwent liver resection for hepatocellular carcinoma or cholangiocarcinoma between 1998-2023 at a tertiary hospital was conducted. ACS-NSQIP predicted risk were compared with observed outcomes using one-sample t-test and chi-squared analysis. Calibration was assessed using Brier scores, and discrimination with the C-statistic. Results: For the 158 consecutive patients, identified the calculator accurately predicted serious complications, sepsis, return to the operating room (ROT), and mortality. It underestimated any complications (30.4% vs 18.9%), cardiac events (7.6% vs 2.0%), venous thromboembolism (7.0% vs 2.5%), and length of stay (3.5 days) but overestimated readmissions (5.1% vs 10.1%) and pneumonia (0.6% vs 3.6%). Calibration was poorest for any complications (Brier 0.249), with acceptable discrimination for ROT (AUC 0.73). Conclusion: The ACS-NSQIP calculator performed reasonably in predicting major complications and mortality following liver resection for primary malignancy. However, minor morbidity is underestimated, hypothesised due to disease- and procedure-specific factors not being adequately captured in the calculator.