Eosinophils are key therapeutic targets in severe asthma as they accumulate in tissues, resulting in local damage through the release of toxic mediators. Benralizumab is a monoclonal antibody with a direct anti-eosinophilic activity that has proved significant clinical efficacy in patients with severe eosinophilic asthma, and its use in real-life went well beyond what we had expected from the pivotal trials, especially in the reduction of asthma exacerbations and oral steroids usage. Benralizumab induces eosinophil apoptosis due to a mechanism of antibody-dependent cell-mediated cytotoxicity by natural killer (NK) cells. Within this review, we will discuss benralizumab pharmacological and pharmacokinetic aspects in the treatment of severe asthma, with an emphasis on the novel immunological effects of benralizumab on NK cells. Overall, these findings account for the clinical efficacy and safety profile of benralizuamb, previously described in patients with an eosinophilic phenotype of the disease.