Asthma has a high healthcare burden globally, with up to 10% of the asthma population suffering from severe disease. Biologic agents are a newer class of asthma treatments for severe asthma, with good evidence for efficacy in clinical trials. Nevertheless, real-world studies of its impact on clinical outcomes are limited. This is an observational cohort study using administrative claims data. The study population consisted of patients aged ≥18 years who had a diagnosis of asthma and initiated mepolizumab after November 4, 2015 and had continuous medical and drug coverage in both the 365 days prior to and following mepolizumab initiation. In patients treated with mepolizumab, we described clinically significant asthma exacerbations by minimum continuous treatment thresholds following initiation of mepolizumab, medication switching patterns and chronic oral corticosteroid (≥28 days) use. We identified 2,536 adults with asthma who initiated mepolizumab. There was an association toward reduction in severe asthma-related events over the first one year of exposure. We observed associations with reduced dispensings of oral corticosteroids over the first year after mepolizumab initiation. Very few patients switched to other biologics during the study period. Treatment with mepolizumab may be associated with fewer asthma-related events in the first year. Over the first one year after initiating mepolizumab, we found associations with decreased concomitant dispensings of oral corticosteroids and medium to high dose ICS/LABA. Additionally, most patients who initiated mepolizumab did not switch to other biologics.