Background: Mepolizumab (MEP) has been recently introduced to treat severe eosinophilic asthma. Trials have demonstrated a significant effectiveness in this asthma phenotype. We evaluated MEP efficacy on lung function, symptoms, asthma exacerbations, biologic markers, steroid dependence and controller treatment level in real-life. Methods: We retrospectively analyzed 134 severe asthmatics (61 males; mean age 58.3 ± 11; mean FEV1%:72 ± 21), treated with MEP for at least 6 months (mean duration:10.9 ± 3.7 months). Results: FEV1% improved significantly after MEP. Mean FEF25-75 also increased from 37.4 ± 25.4% to 47.2 ± 27.2% (p < 0.0001). Mean baseline blood eosinophil level was 712 ± 731/μL (8.4 ± 5.2%) decreasing to 151 ± 384/μL (1.6 ± 1.6%) (p < 0.0001), FENO levels decreased likewise. MEP treatment also led to a significant ACT improvement (mean pre:14.2 ± 4.4; mean post:20.5 ± 28) and exacerbations significantly fell from 3.8 ± 1.9 to 0.8 ± 1.1 (p < 0.0001). 74% of patients were steroid-dependent before MEP. 45.4% and 46.4% of them showed a suspension and dose reduction respectively (p < 0.0001). A significant number reduced also ICS doses. Only 67% of subjects used SABA as needed before MEP, falling to 20% after MEP. About 40% of patients highlighted a maintenance therapy step-down. Subjects showing an omalizumab treatment failure before MEP had a similar positive response when compared with omalizumab untreated patients. Conclusion: In real-life, MEP improved significantly all outcomes even small airway obstruction, suggesting its possible role also in distal lung region treatment. Furthermore, it demonstrated its high effectiveness in OC/ICS-sparing, in reducing SABA as needed and in stepping-down maintenance therapy. MEP is a valid alternative for patients with previous omalizumab treatment failure.