An analysis of Auckland City Hospital Adult Emergency Department (ED) data has shown that Māori are less likely to have a diagnosis recorded at discharge than non-Māori, due to systemic bias in how diagnoses are captured electronically. A total of 5788 visits to the ED (n = 594 Māori, 5194 non-Māori) were audited in February 2021. In a random sample of case notes (n = 114), diagnoses recorded by clinicians were compared with diagnoses derived from clinical notes by auditors blinded to the actual diagnosis, patient name, and ethnicity. The New Zealand Emergency Department SNOMED-CT reference set was used to code diagnoses. Māori were less likely to have a diagnosis recorded at ED discharge compared with non-Māori (relative risk 1.48, 95% confidence interval 1.08-2.04, p = 0.016). Failure to record diagnoses was the result of a system flaw in extracting diagnoses from electronic notes, rather than failure to make a diagnosis. There was agreement in diagnoses recorded by clinicians and auditors for 94.6% of cases in Māori and 100% of those in non-Māori.