OBJECTIVE This study aimed to investigate the demographic differences amongst patients diagnosed with infective endocarditis (IE), predictors of adverse events, and the association between clinical decision-making and adverse health outcomes amongst patients with IE. METHODS A retrospective cross-sectional study was conducted using the New South Wales (NSW) Admitted Patient Data Collection (APDC) from the Centre for Health Record Linkage (CHeReL). METHODS All patients (N=18,044) from 2001 to 2020 in New South Wales who received a diagnosis of IE using ICD-10-AM diagnostic code 133.0 were included. METHODS Categorical variables were compared using the chi-square test or Fisher's exact test, while the t-test was used for continuous variables. The association between clinical decision-making and adverse health outcomes amongst patients with IE were examined via generalised linear mixed models. RESULTS Sex, age, birthplace and referral impacted clinical decision-making, in-hospital death and severity of the disease. Women experienced a higher risk of death and fewer escalations of care. Admission and mortality increased with age, with those aged 60 years and above responsible for 60.8% of hospitalisations. Despite octogenarians making up one-fifth of admissions and having the worst mortality rate (15.1%), they experienced only one in 10 intensive care (ICU) admissions. Overseas-born patients had fewer escalations of care and experienced less severe disease if referred by a medical practitioner. One out of 10 admissions that resulted in a hospital death were given non-emergency status, and one in two ICU patients died in hospital. CONCLUSIONS Sex, age, place of birth, and clinical decision-making were important predictors of severe disease and death in hospital, lending weight that health care clinical decisions may adversely impact health outcomes for populations of interest.