Diabetes mellitus (DM) patients are at an increased risk of acute myocardial infarction (AMI). Adequate DM control may reduce in-hospital mortality and cardio-pulmonary complications after an AMI. The objective of this study was to determine whether uncontrolled DM in patients with an incidental AMI was associated with an increased risk of in-hospital mortality and selected cardio-pulmonary complications. A secondary data analysis of the Puerto Rican Cardiovascular Surveillance System during 2007, 2009, and 2011 was conducted. The study included men and women living in Puerto Rico who were hospitalized due to an incidental AMI and had information on HbA1cmeasurement (n=220). Patients were divided according to their HbA1c levels into two groups (i) <7% (controlled); and (ii) >7% (uncontrolled). Mortality and complications were defined according to ICD-9 codes. Univariate and multivariate logistic regression models were used to test for associations between HbA1c and mortality and cardio-pulmonary outcomes. The model was adjusted for gender, obesity (BMI >30kg/m2), hyperlipidemia, hypertension, chronic obstructive pulmonary disease, smoking, insurance and age. The results revealed no statistically significant association between the controlled and the uncontrolled DM patients and mortality, respectively cardiopulmonary complications (unadjusted OR 2.1; 95% CI: 0.7-6.4; adjusted OR 2.4; 95% CI: 0.5-10.5). The uncontrolled DM group was statistically significantly younger than those with controlled DM (mean age 65.2 vs. 71.1 years; p-value 0.002). There was no statistically significant difference in the prevalence of uncontrolled DM between patients with complications (80%) and those without complication (66%; p=value 0.203). AMI patients with uncontrolled DM did not have an increased risk of mortality and cardiopulmonary complications compared to patients with controlled DM. This needs further evaluation in a larger study population and DM patients with an AMI should have HbA1c measured to estimate their risk of complications.