Background: Bronchiectasis and asthma are different in many respects, but some patients have both conditions. Studies assessing the effect of bronchiectasis on asthma exacerbation are rare. The aim of this study is to investigate the effect of bronchiectasis on asthma exacerbation. Methods: We enrolled 2,270 asthma patients who were followed up in our hospital. Fifty patients had bronchiectasis and asthma. We selected fifty age- and sex-matched controls from the 2,220 asthma patients without bronchiectasis, and assessed asthma exacerbation and its severity based on the annual incidence of total asthma exacerbation, annual prevalence of steroid use, and frequency of emergency room visits and hospitalizations due to asthma exacerbation in each group. Results: Fifty patients (2.2%) had bronchiectasis and asthma. The annual incidence of asthma exacerbation was higher in patients with asthma and bronchiectasis than in patients with asthma alone ($1.08{pm}1.68$ vs. $0.35{pm}0.42$, p=0.004). The annual prevalence of steroid use ($0.9{pm}1.54$ vs. $0.26{pm}0.36$, p=0.006) and the frequency of emergency room visits ($0.46{pm}0.84$ vs. $0.02{pm}0.13$, p=0.001) due to asthma exacerbation were also higher in patients with asthma and bronchiectasis than in patients with asthma alone. Conclusion: Bronchiectasis is associated with difficult asthma control.