Background Following myocardial infarction, medication is, besides lifestyle interventions, the cornerstone treatment to improve survival and minimize the occurrence of new cardiovascular events. Still, data on nationwide medication adherence are scarce. This study assesses medical adherence during one year following myocardial infarction, stratifying per type of infarct, age and gender. Design Retrospective cohort study. Methods In The Netherlands, all inhabitants are by law obliged to have health insurance and all claims data are centrally registered. In 2012 and 2013, all national diagnosis-codings of ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) were acquired. Furthermore, information on retrieved medication was extracted from the Dutch Pharmacy Information System. Twelve months after discharge, the retrieved medication at the pharmacy of each pharmacological therapy (aspirin-species, P2Y12-inhibitor, statin, beta-blocker, angiotensin-converting enzyme-/angiotensin 2-inhibitor, vitamin-K antagonists or novel oral anticoagulant) were analysed. Results In total, 59,534 patients (67 ± 13 years, 39,545 (66%) male, 57% NSTEMI) were included, of whom 52,672 (88%) patients were analysed for one-year medical adherence. STEMI patients more often achieved optimal medical adherence than NSTEMI patients (60% vs. 40%, p ≤ 0.001). In both STEMI and NSTEMI, use of all five indicated drugs was higher in male patients compared with female (STEMI male 61% vs. female 57%, p ≤ 0.001; NSTEMI male 43% vs. female 37%, p ≤ 0.001. With increasing age, a gradual decrease was observed in the use of aspirin, P2Y12-inhibitors and statins. Conclusion Age and gender differences existed in medical adherence after myocardial infarction. Medical adherence was lower in women, young patients and elderly patients, specifically in NSTEMI patients.