Using a new-generation drug-eluting stent, we compared the 2-year clinical outcomes of patients with diabetes mellitus (DM) and non-DM concomitant with a non-ST-segment elevation myocardial infarction (NSTEMI) and an ST-segment elevation myocardial infarction (STEMI) who underwent percutaneous coronary intervention. A total of 11,798 patients with acute myocardial infarction were classified into two groups: DM (NSTEMI, n = 2399; STEMI, n = 2693) and non-DM (NSTEMI, n = 2694; STEMI, n = 4012). The primary clinical outcome was the occurrence of major adverse cardiac events (MACE), defined as all-cause death, recurrent myocardial infarction, or any coronary repeat revascularization. The secondary outcome was the occurrence of definite or probable stent thrombosis. In all the patients, both multivariable and propensity score-adjusted analyses revealed that the incidence rates of MACE (adjusted hazard ratio (aHR), 1.214; p = 0.006 and aHR, 1.298; p = 0.002, respectively), all-cause death, cardiac death (CD), and non-CD rate were significantly higher in the NSTEMI group than in the STEMI group. Additionally, among patients with NSTEMI, there was a higher non-CD rate (aHR, 2.200; p = 0.007 and aHR, 2.484; p = 0.004, respectively) in the DM group and a higher CD rate (aHR, 2.688; p < 0.001 and 2.882; p < 0.001, respectively) in the non-DM group. In this retrospective study, patients with NSTEMI had a significantly higher 2-year mortality rate than those with STEMI did. Furthermore, strategies to reduce the non-CD rate in patients with DM and the CD rate in patients without DM could be beneficial for those with NSTEMI.