Background: The American Diabetes Association (ADA) recommends low-dose aspirin therapy as a primary prevention strategy in patients with type 1 or type 2 diabetes mellitus (DM) at increased cardiovascular risk. However, not all patients who are indicated are taking aspirin therapy, and it is not routinely documented in the electronic health record (EHR). Objective: To determine frequencies of appropriate aspirin use and documentation in the EHR in adult patients with DM. Methods: Adult patients with DM were randomized and contacted for participation in a telephonic survey between January and October 2013. Patients who consented were administered a standardized oral telephone survey regarding aspirin use. Patient demographics, current medications, allergies, past medical history, and pertinent laboratory values were collected. Patients were then stratified by the ADA-defined indication for aspirin. The primary outcomes were rates of appropriate aspirin use and documentation of aspirin therapy in the EHR. Results: Investigators contacted 276 patients for inclusion. Of the 81 patients surveyed, 74% were indicated for aspirin therapy. Nearly all (92.3%) patients reporting aspirin use were indicated for aspirin therapy compared with only 57.1% of patients who did not report aspirin but were indicated (P = 0.0003). Alternatively, 96.7% of patients with aspirin use documented in their EHR were indicated for aspirin therapy compared with only 60.8% of patients who did not have aspirin use documented in the EHR but had an indication (P = 0.0002). Approximately 20% of the patients indicated for and reporting aspirin use did not have aspirin documented in their EHR. Conclusions: Aspirin use in patients with DM who are indicated for therapy is significantly underutilized and underdocumented.