We evaluated variation in treatment for, and outcomes following, myocardial infarction (MI) by diabetes status, sex and socioeconomic disadvantage.We included all people aged ≥30 years who were discharged alive from hospital following MI between 1 July 2012 and 30 June 2017 in Victoria, Australia (n=43 272). We assessed receipt of inpatient procedures and discharge dispensing of cardioprotective medications for each admission, as well as 1-year all-cause, cardiovascular, and MI readmission rates and 1-year all-cause mortality.Risk of all-cause (HR: 1.22 (1.19-1.26)), cardiovascular (1.29 (1.25-1.34)), MI (1.52 (1.43-1.62)) and heart failure readmission (1.62 (1.50-1.75)) and mortality (1.18 (1.11-1.26)) were higher in people with diabetes. Males and people in more disadvantaged areas were at increased risk of readmission and mortality following MI. People with diabetes (vs without) were more likely to receive coronary artery bypass grafting (CABG) but less likely to receive percutaneous coronary intervention (PCI) during, or within 30 days of, their index admission. Females were less likely to receive either (eg, 87% of males with a STEMI received PCI or CABG vs 70% of females), and people in more disadvantaged areas were less likely to receive PCI. People with diabetes, males and people in more disadvantaged areas were more likely to be dispensed cardioprotective medications at or within 90 days of discharge.Following an MI, people with diabetes and males had poorer outcomes but received more intensive cardiovascular treatments. However, socioeconomic disadvantage was associated with both less intensive inpatient treatment and poorer outcomes.