Background: Patients with diabetes mellitus (DM) have a high risk for cardiovascular disease (CVD) events after an acute myocardial infarction (AMI). High-intensity statins reduce CVD risk following AMI among patients with and without DM. Methods: We determined the proportion of Medicare beneficiaries 66 to 75 years of age taking a low/moderate-intensity statin with (n = 6718) and without (n = 6414) DM who titrated to a high-intensity statin dosage (i.e., atorvastatin 40 or 80 mg, or rosuvastatin 20 or 40 mg) following an AMI hospitalization in 2014–2015. All patients had a pharmacy claim for a statin fill within 365 days prior to, and within 30 days after their AMI hospitalization. We excluded beneficiaries without Medicare fee-for-service coverage including pharmacy benefits during the study period and those with a pharmacy claim for a high-intensity statin prior to their AMI. Results: The first statin fill following hospital discharge was for a high-intensity dosage among 37.7% and 44.4% of patients with and without DM, respectively. After multivariable adjustment, the risk ratio (RR) for titrating to a high-intensity statin comparing patients with versus without DM was 1.01 (95% CI 0.96, 1.06). Among patients whose first statin fill post-AMI was for a low/moderate-intensity dosage, 7.5% of those with DM titrated to a high-intensity statin within 182 days, compared with 9.2% of those without DM (multivariable-adjusted RR 0.90 [95% CI 0.75, 1.08]). Conclusions: Most patients taking a low/moderate-intensity statin were not titrated to a high-intensity dosage following AMI irrespective of their diabetes status, potentially leaving substantial residual risk for recurrent CVD events.