Purpose The incidence of cognitive impairment is high in elderly patients with airway disease. However, the impact of cognitive function on inhaler competence is unclear. The aim of the study was to determine the relation between cognitive assessment score (K-MMSE) and inhaler competence in elderly patients of airway disease. Methods This prospective observational study was performed in a tertiary care university hospital in South Korea from January 2019 to September 2020. Inhaler naive patients aged ≥60 years diagnosed of airway disease were enrolled. The type of inhaler prescribed was determined by clinician. K-MMSE and inhaler performance score was assessed on the day inhaler was first prescribed (V0). Feedback education on error observed during inhaler performance assessment was given after the assessment was finished. On follow up visit (V1) after 1-3 months from V0, the inhaler performance was assessed again. The correlation between the K-MMSE score and inhaler performance score was analyzed by Pearson correlation test. Results Total 108 patients were enrolled. Median age was 69.0 (66.0-76.0) and 82 (75.9%) were male. Mean duration of education was 10.0 years and median K-MMSE score was 28.0. Inhaler technique accuracy was lower at V0 than at V01 (76.9% vs 100%, P < 0.001). Significant positive correlation was observed between K-MMSE score and inhaler technique accuracy at both V0 and V1 assessment (r=0.341, P < 0.001; r=0.217, P=0.048, respectively). Among the sub-cognitive functions of K-MMSE, registration, recall and place orientation showed significant correlation with inhaler performance score at V0 (r=0.222, P=0.021; r=0.254, P=0.008; r=0.278, P=0.004; respectively). At V1, attention and calculation showed significant correlation with inhaler performance score (r=0.300, P=0.006) Conclusions Inhaler technique accuracy was impaired as the K-MMSE score was lower in elderly patients with airway disease. However, by giving feedback education on error, accuracy was improved.