Background. The control of severe bronchial asthma, such as corticosteroid-resistant asthma, is difficult. It is also possible that immunosuppressive agents would be effective for bronchial asthma. Case Summary. A 55-year-old Japanese female presented with severe bronchial asthma controlled with tacrolimus. She had been diagnosed with bronchial asthma during childhood. Her asthma worsened, and a chest radiograph showed atelectasis of the left lung. Bronchoscopy revealed the left main bronchus to be obstructed with viscous sputum consisting of 82% neutrophils and no eosinophils. The atelectasis did not improve with corticosteroid treatment, but was ameliorated by administration of tacrolimus. Discussion. This patient had severe asthma due to neutrophilic inflammation of the airways. Tacrolimus is effective for treating severe asthma, for example, in corticosteroid-resistant cases.