Background Severe asthma with fungal sensitisation (SAFS) and allergic bronchopulmonary aspergillosis (ABPA) are important complications of severe asthma. The evidence for treating them with omalizumab is limited. Objective To determine the effectiveness of treatment with omalizumab in severe allergic asthma patients comparing those with and without evidence of fungal sensitisation using data recorded in the Australian Xolair registry. Methods Data from 205 patients who received omalizumab and recorded in the Australian Xolair Registry was analysed to determine change in Asthma Control Questionnaire (ACQ-5) score, exacerbation frequency, and oral corticosteroid (OCS) dosage over a 24 month period of omalizumab treatment. Patients were grouped into cohorts based on fungal sensitisation and an analysis of improvement in outcomes between baseline and 24 months was conducted within each group. A further subgroup analysis of patients with ABPA was also conducted. Results Patients with severe asthma and fungal sensitisation (n=62), including those with ABPA (ASAFS), were as likely to demonstrate significant improvements to omalizumab in ACQ-5, exacerbations and reduced regular OCS dose over 24-months as those with severe asthma without sensitisation to fungi (n=156). After adjusting for age, sex, BMI, smoking history and baseline FEV1% the effects still remained. A subgroup analysis of 11 ABPA patients similarly demonstrated a significant improvement on omalizumab. Conclusion Omalizumab is an effective therapy in ASAFS, leading to sustained improvements in symptoms and exacerbations for 24 months. The benefit for ABPA is less clear due to the small sample. .