The effect of a history of cancer on the prognosis of patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI) is poorly understood.From the Osaka Acute Coronary Insufficiency Study (OACIS) registry in Osaka, Japan, we enrolled the case data of a total of 3499 patients with AMI treated with PCI between 1998 and 2014, of whom 462 had a cancer history (cancer group, 13.2%) and 3037 did not (non-cancer group, 86.8%). All of the cases were followed for up to five years from discharge.The Kaplan-Meier curve and multivariate analysis using Cox proportional hazards models revealed that all-cause mortality was significantly higher in the cancer group than in the non-cancer group (adjusted hazard ratio [HR], 2.43; P < 0.001). Deaths from cardiac, cancer, and other causes were treated as competing events, and competing analysis using the cumulative incidence function (CIF) and Fine-Gray model revealed that mortality due to cancer was higher in the cancer group than in the non-cancer group, whereas cardiac mortality was similar between the two groups. The incidences of cardiovascular events, including stroke, recurrent infarction, and heart failure requiring readmission, were also similar between the two groups, although the Kaplan-Meier analysis and univariate Cox proportional hazards model revealed that the incidence of stroke was higher in the cancer group than in the non-cancer group.A history of cancer increased all-cause and cancer mortality among patients with AMI treated with PCI, although it was not associated with cardiovascular events.