Background Evidence of the cardiovascular benefits of adherence to quality indicators in diabetes care over a period of years is lacking. Methods and Results We conducted a population‐based, historical cohort study of 105 656 people aged 45 to 80 with pharmacologically treated diabetes and who were free of cardiac disease in 2010. Data were retrieved from electronic medical records of the 4 Israeli health maintenance organizations. The association between level of adherence to national quality indicators (2006–2010: adherence assessment) and incidence of cardiac outcome; ischemic heart disease or heart failure (2011–2016: outcome assessment) was estimated using Cox proportional hazards models. During 529 551 person‐years of follow‐up, 19 246 patients experienced cardiac disease. An inverse dose–response association between the level of adherence and risk of cardiac morbidity was shown for most of the quality indicators. The associations were modified by age, with stronger associations among younger patients (<65 years). Low adherence to low‐density lipoprotein cholesterol testing (≤2 years) during the first 5 years was associated with 41% increased risk of cardiac morbidity among younger patients. Patients who had uncontrolled low‐density lipoprotein cholesterol in all first 5 years had hazard ratios of 1.60 (95% CI, 1.49–1.72) and 1.23 (95% CI, 1.14–1.32), among patients aged <65 and ≥65 years, respectively, compared with those who achieved target level. Patients who failed to achieve target levels of glycated hemoglobin or blood pressure had an increased risk (hazard ratios, 1.50–1.69) for cardiac outcomes. Conclusions Longitudinal adherence to quality indicators in diabetes care is associated with reduced risk of cardiac morbidity. Implementation of programs that measure and enhance quality of care may improve the health outcomes of people with diabetes.