Few studies have assessed the relationships between xerostomia and the use of inhaled corticosteroids (ICS). The main objective of this study was to investigate the prevalence of xerostomia in a respiratory outpatient clinic and its relationship with bronchial asthma and ICS use. A cross-sectional observational study of patients recruited in an outpatient setting divided them according to previous diagnoses of bronchial asthma. Data about pulmonary function, concomitant medication, medical comorbidities, Xerostomia Inventory test (XI test), and the degree of asthma control by ACT (asthma control test) were collected for each patient. A linear regression model was applied, using the XI score as dependent variable and the ACT score as independent variable. The 57 patients were divided into asthmatics (40 patients, 70.2%) and control group without asthma (17, 29.8%). The prevalence of xerostomia was 87.7% (50 patients), with no differences between the study groups or current dose of ICS. In the asthmatic group, patients with uncontrolled asthma had worse XI scores than those with partially or totally controlled asthma (30.43 ± 8.71 vs. 24.92 ± 8.08; P < 0.05). In a logistic regression model, the XI test was significantly associated to ACT scores with a moderately strong correlation (r = 0.55; P = 0.005) after adjusting for the current daily dose of ICS. Xerostomia is a common symptom in the ambulatory setting. There is a moderate relationship between the degree of asthma control and the severity of xerostomia.