Objectives/Hypothesis It is not unequivocally proven whether a combination of an intranasal corticosteroids (INSs) and a cysteinyl leukotriene receptor antagonist has greater efficacy than INSs in the treatment of seasonal allergic rhinitis (SAR). Study Design Single-center, randomized, open-label study. Methods Study subjects included 46 participants with SAR. Participants were randomized to receive budesonide (BD; 256 mu g) plus montelukast (MNT; 10 mg) (BD + MNT) or BD alone (256 mu g) for 2 weeks. Visual analog scale scores for five major symptoms of SAR, nasal cavity volume (NCV), nasal airway resistance (NAR), and fractional exhaled nitric oxide (FeNO) were assessed before and at the end of treatments. Results Both treatments significantly improved the five main SAR symptoms from baseline; however, BD + MNT produced significantly greater improvements in nasal blockage and nasal itching compared to BD alone. At baseline, the nasal blockage score was significantly correlated with NCV and NAR (r = -0.473, P = .002 and r = -0.383, P = .013, respectively). After 2 weeks of treatment, BD + MNT significantly improved NCV, but not NAR, to a greater level than BD. The number of patients with FeNO concentration >= 30 ppb at baseline was significantly decreased after BD + MNT treatment, but not after BD treatment. Similarly, BD + MNT treatment led to a significantly greater decrease in FeNO concentration than BD treatment. Conclusions BD + MNT treatment may have an overall superior efficacy than BD monotherapy for patients with SAR, especially in improvement of nasal blockage, itching, and subclinical lower airway inflammation. Also, NCV and NAR could be used to assess nasal blockage more accurately. Level of Evidence 1b Laryngoscope, 2019