Background: Asthma and bronchiectasis are critical diseases for public health. In some patients, asthma and bronchiectasis exist together, and bronchiectasis negatively affects asthma control. This study aimed to evaluate the clinical impacts of coexisting asthma and bronchiectasis on patients. Methods: This was a retrospective single-center study on data collected from electronic medical records between January 2014 and January 2017. Patients were divided into three groups, wherein asthma (n = 33), bronchiectasis (n = 33), and coexisting asthma and bronchiectasis (n = 33) were compared. Asthma diagnosis was made according to the guidelines of Global Initiative for Asthma. Confirmation of bronchiectasis diagnosis was made by high-resolution computed tomography. Patients with cystic fibrosis and those who have asthma–chronic obstructive pulmonary disease overlap syndrome were excluded from the study. Results: Medical records of 1467 patients were analyzed. Among them, well-matching 99 patients in terms of gender and comorbid diseases were taken (33 of them had only asthma, 33 had only bronchiectasis, and 33 had coexisting asthma and bronchiectasis). Forty (40.5%) men and 59 (59.5%) women with a mean age of 45.0 ± 5.2 were included in the study. Asthma and bronchiectasis coexistence had lower forced expiratory volume in 1 s (FEV1) (%), forced vital capacity (FVC) (%), FEV1/FVC (%), and FEV1 (L) ratios (P = 0.0001). Moreover, total immunoglobulin E levels were the highest in this group (P = 0.0001). The most frequently observed microorganism in the culture tests was Pseudomonas aeruginosa in the bronchiectasis-only as well as in asthma + bronchiectasis groups. Conclusions: Asthmatic patients who have bronchiectasis revealed lower asthma control levels and worse respiratory function test results than other groups.