Background: Although inhaled corticosteroids (ICSs) are the recommended first-line therapy for asthma, determining whether to continue or discontinue ICS treatment in patients with mild asthma remains challenging for clinicians. Several studies have revealed that patients with mild-persistent asthma maintained a well-controlled state after ICS withdrawal. However, the long-term outcomes of ICS withdrawal have not yet been determined. Objective: To determine the possible clinical outcomes of the discontinuation of ICS in patients with well-controlled mild asthma. Methods: We investigated the clinical outcomes of discontinuing ICSs in patients with well-controlled mild asthma and compared the time to loss of control (LOC) between patients who stopped ICS treatment (ICS withdrawal group, IWG) and those who continued treatment for 3 years (continuous ICS group, CIG). Results: A significant difference in the time to LOC was observed between the IWG and CIG (hazard ratio, 2.56; 95% confidence interval, 1.52-4.33; P <.001). Increasing fractional exhaled nitric oxide levels (P = 0.008) and sputum eosinophil counts (%) (P = 0.015) revealed a weak but significant association with LOC risk in the CIG. The sputum eosinophil counts (P = 0.039) and serum total immunoglobulin E levels (P = 0.014) were significantly higher in the LOC group than in the non-LOC group of the CIG. Conclusion: Our results suggest that the maintenance of ICS treatment may help keep patients’ asthma under control. Furthermore, patients with LOC had significantly higher sputum eosinophil counts in the CIG than those in the non-LOC group. Therefore, continuous ICS use by patients with mild, well-controlled asthma could be associated with good clinical outcomes. Trial Registration: ClinicalTrials.gov Identifier: KCT0002234.