The clinical efficacy of glucagon-like peptide-1 (GLP-1) analogs in patients with acute myocardial infarction (AMI) is uncertain. The purpose of the present study was to evaluate the effects of the GLP-1 analog liraglutide on left ventricular (LV) remodeling in patients with AMI. We retrospectively evaluated the effects of liraglutide on LV remodeling assessed by cardiac magnetic resonance imaging (CMRI) in 15 patients with type 2 diabetes who were successfully treated with primary percutaneous coronary intervention (PCI) for AMI. Patients were divided into two groups based on their hypoglycemic medication: liraglutide use (group L; n = 6) or standard therapy (group S; n = 9). The CMRI findings in the early phase and at the 6-month follow-up were compared. At the 6-month follow-up, group S showed increases in LV end-diastolic (from 64 to 74 mL/m², p = 0.08) and end-systolic (from 38 to 45 mL/m², p = 0.13) volume indexes, whereas no such increase was observed in group L. The LV mass index (LVMI) was significantly smaller in group L than in group S at baseline (64 vs. 75 g/m², p = 0.05) and at follow-up (56 vs. 78 g/m², p = 0.009). Multivariate regression analysis showed that liraglutide use was an independent negative predictor of LVMI (β = −0.720, p = 0.003). In conclusion, liraglutide may be able to prevent the progression of LV remodeling and is associated with a lower LV mass in diabetic patients with AMI undergoing primary PCI.