Rationale: Allergic rhinitis and exercise induced bronchoconstriction (EIB) are common in asthmatic children. The aim of this study was to investigate whether treatment of allergic rhinitis with an intranasal corticosteroid protects against EIB in asthmatic children. Methods: This was a double-blind, randomized, placebo-controlled, parallel group study. Subjects aged 12–17 years, with mild-to-moderate asthma, intermittent allergic rhinitis and ≥10% fall in FEV1 at a screening exercise challenge were randomized to 22 ± 3 days treatment with intranasal fluticasone furoate or placebo. The primary outcome was change in exercise induced fall in FEV1. Secondary outcomes were changes in the area under the curve (AUC), asthma control questionnaire (ACQ), pediatric asthma quality of life questionnaire (PAQLQ), and exhaled nitric oxide (FeNO). Results: Twenty-five children completed the study. Mean exercise induced fall in FEV1 (±SD) decreased significantly (95% CI: 0.7–18.2%, P = 0.04) in the fluticasone furoate group from 28.4 ± 15.8% to 19.0 ± 13.8%, compared to the placebo group (27.4 ± 16.0% to 27.4 ± 19.2%). The change in AUC was not significantly different between treatment groups. However, within the fluticasone furoate group the AUC decreased significantly (P = 0.01). Although total PAQLQ score did not improve, the activity limitation domain score improved significantly within the fluticasone furoate group (P = 0.03). No significant changes were observed in FeNO and ACQ. Conclusion: Treatment of allergic rhinitis in asthmatic children with an intranasal corticosteroid reduces EIB and tends to improve quality of life. Pediatr Pulmonol. 2012; 47:27–35.