Background: Adherence to recommended medications is a key issue in the care of patients with cardiovascular disease (CVD) and barriers to adherence are well established during the medication adherence cascade, the processes of prescribing, obtaining, taking, and maintaining medication use. Aspirin avoids many of the barriers in the medication adherence cascade as it does not require a prescription (prescribing) and is inexpensive, easily accessible (obtaining), prescribed once-daily (taking) as an over-the-counter medication and is generally perceived by patients as safe (maintaining). The purpose of this paper is to report aspirin adherence and propose the Medication Adherence Cascade Tool to assist clinicians to consider all aspects of medication adherence. Methods: Adherence to aspirin was monitored with an electronic pillbox. Frequency analysis, independent T-tests, and ANOVA were completed on 151 patients with underlying heart failure who were prescribed aspirin within a larger parent study. Chi-square tests were completed to assess differences in baseline demographic characteristics. Findings: Mean aspirin adherence was 82.2% overall, with 11.9% of sample with adherence 50%, 18.5% with adherence 50-80%, and 69.5% with adherence ≥80%. Greater adherence was observed in self-identified White as compared to Black patients (84.47% vs 73.53%; p = 0.014), and patients ≥70 years of age compared to <70 years (87.00% vs 77.49%; p = 0.009). Interpretation: Aspirin adherence was suboptimal despite the fact that it addresses most of the barriers on the medication adherence cascade (ie, relatively easy access, low cost, and low risk). A Medication Adherence Cascade Tool (MACT) is proposed as a clinical guide to facilitate patient-provider co-production of strategies to address medication adherence. The tool can assist patients and providers to co-produce adherence to achieve optimal medication benefits.