We evaluated if budesonide inhalation suspension (BIS) reduces the immunogenicity of the varicella vaccine in paediatric patients with asthma. This open-label, parallel-group, cohort study included varicella-naïve (disease and vaccine) children aged 12 months to 8 years with asthma requiring therapy. Patients who received ≥ 4 weeks of asthma treatment with BIS 0.25–1 mg daily or non-steroidal conventional asthma therapy (NSCAT) daily or as needed and met eligibility requirements received the varicella vaccine (Varivax®) and continued the same asthma treatment for ≥ 8 weeks postvaccination. Varicella-zoster virus (VZV) antibody levels were assessed before and 6 weeks after vaccination using a glycoprotein enzyme-linked immunosorbent assay (gpELISA). Adverse events (AEs) were assessed throughout the study. Antibody levels were analysed in 243 of 274 patients who were vaccinated and received treatment. After immunisation, the percentage of patients in each group achieving a ‘protective’ level of VZV antibody (≥ 5 gpELISA units/ml) was similar: 85% (129/151) in the BIS group and 90% (83/92) in the NSCAT group (relative risk = 0.95; 95% confidence interval 0.86–1.04). Eight patients in each group reported AEs related to varicella vaccination (primarily pyrexia, agitation and injection-site reactions). There were no cases of severe varicella in either group; one case of mild varicella-like rash was reported in a 12-month-old child in the NSCAT group 11 days after vaccination. VZV antibody responses and tolerability to the live varicella vaccine in paediatric asthma patients treated with BIS vs. NSCAT were comparable, demonstrating that young children with asthma receiving nebulised BIS can be immunised effectively with Varivax.