Mepolizumab was recently approved for treating Chronic Rhinosinusitis with Nasal Polyps (CRSwNP) unresponsive to standard treatment or recurring after endoscopic sinus surgery (ESS). To date, few studies have assessed Mepolizumab's efficacy in severe type-2 CRSwNP. Our study aimed to analyze sinonasal outcomes in type-2 CRSwNP patients treated with 100mg Mepolizumab administered subcutaneously every four weeks. We conducted a retrospective study of patients with severe, recalcitrant CRSwNP treated with Mepolizumab. Demographic and clinical characteristics were collected, including age, sex, and comorbidities such as asthma, nonsteroidal anti-inflammatory drug-exacerbated respiratory disease (NERD), and allergic rhinitis (AR), as well as the number of previous ESS procedures and the interval since the last one. Patients were evaluated at baseline and after one year for blood eosinophil count, nasal polyp score (NPS), modified Lund-Kennedy score (mLKS), olfactory function (using a VAS scale and a 16-item Sniffin' identification test), SNOT-22, and sinus opacification on CT scans. The need for rescue ESS or systemic corticosteroids (SCS), response to treatment, and side effects were also recorded. Data from 27 patients were collected. After one year, all scores showed significant improvement. NERD was the only factor associated with a less favorable improvement in olfactory function. There were no side effects reported, although 2 patients discontinued Mepolizumab as they were considered "non-responders." Mepolizumab is safe and effective in reducing the clinical, endoscopic, and radiological burden of disease, as well as in decreasing the need for salvage ESS or systemic steroids.