Objective To analyze the factors influencing medication adherence in elderly patients with diabetes mellitus (DM) and hypertension (HTN) by constructing a retrospective cohort study. Methods To retrospectively analyze the clinical data of 147 elderly patients with DM and HTN admitted to Zhengzhou Jinshui District General Hospital from April 2022 to April 2024, and classify them into good and poor groups according to their medication adherence, collect and compare the patients’ general information and laboratory indexes, and incorporate the indexes with differences between the two groups into the logistic regression model to explore the factors influencing the medication adherence of elderly patients with DM and HTN. And the predictive value of the factors on medication adherence in elderly patients with DM and HTN was analyzed by plotting nomograms and calibration curves. Results A total of 147 elderly patients with DM and HTN were included in this study, of which 30 patients with medication adherence score<6 were included in the poor group, accounting for 20.41%, and 117 patients with medication adherence score ≥ 6 were included in the good group, accounting for 79.59%; there were differences among the study subjects in terms of age, memory function, psychological status, literacy level, and health education (P<0.05); in the results of the multifactorial logistic regression analysis, age, memory function, psychological status, literacy, and health education were all influential factors for poor medication adherence in elderly patients with DM and HTN; it was found that age, memory function, psychological status, literacy, and health education had higher values in predicting medication adherence in elderly patients with DM and HTN by plotting nomograms and calibration curves, and the calibration curves were similar to the standard curves, suggesting that the column line graphs had good consistency. Conclusion Medication adherence in elderly patients with DM and HTN is affected by age, memory function, psychological status, literacy and health education, and clinical intervention can be carried out in a timely manner according to the above factors, with a view to improving medication adherence in elderly patients with DM and HTN.