ObjectiveMetabolic dysfunction‐associated steatotic liver disease (MASLD) and obesity increases risk of cardiovascular disease. This cohort study examines the prognostic value of MASLD, across body weight categories, in a secondary preventative acute myocardial infarction (AMI) cohort.MethodsPatients with AMI were stratified into four phenotypes—obesity MASLD, non‐obesity MASLD, obesity non‐MASLD, non‐obesity non‐MASLD. The primary outcome was all‐cause mortality. Cox regression analysis was performed to investigate determinants of long‐term all‐cause mortality.ResultsOf 5702 patients, majority were in the non‐obesity non‐MASLD group (66.7%), followed by obesity MASLD (16.1%), non‐obesity MASLD (11.2%) and non‐obesity MASLD (6.0%). Across the four phenotypes, obesity MASLD had the highest cardiometabolic burden, followed by non‐obesity MASLD. Non‐obesity MASLD had the highest risk of heart failure (p = 0.034), cardiogenic shock (p < 0.001), and all‐cause long‐term mortality (p = 0.019). The non‐obesity MASLD (HR 1.400, 95%CI 1.077–1.820, p = 0.012) and obesity MASLD phenotypes (HR 1.222, 95%CI 1.005–1.485, p = 0.044) were independently associated with long‐term all‐cause mortality.ConclusionsObesity and non‐obesity MASLD phenotypes were predictors of all‐cause mortality following AMI, with an even larger magnitude of mortality risk in the non‐obesity MASLD group. The recognition of MASLD and its body weight phenotypes will be beneficial in the prognostication following AMI.