Many patients with allergic rhinitis (AR) have uncontrolled symptoms despite available treatment options. This study was designed to evaluate the efficacy and safety of MP29-02 (a novel intranasal formulation of fluticasone propionate [FP] and azelastine [AZ] hydrochloride), compared with monotherapy with FP, AZ, and placebo sprays for the treatment of seasonal allergic rhinitis (SAR). This 2-week randomized, double-blind, placebo-controlled trial was conducted in 779 patients with moderate-to-severe SAR. Treatments were administered 1 spray/nostril twice daily in the same vehicle and delivery device. Daily doses of AZ and FP were 548 and 200 micrograms, respectively. The primary efficacy variable was the 12-hour reflective total nasal symptom score (rTNSS), consisting of nasal congestion, sneezing, itchy nose, and runny nose. Secondary efficacy variables were (1) 12-hour reflective individual nasal symptom scores; (2) onset of action; (3) 12-hour reflective total ocular symptom score (rTOSS), including itchy eyes, watery eyes, and red eyes; and (4) the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) overall score. MP29-02 significantly reduced the mean rTNSS from baseline by -5.54 points compared with FP (-4.55; p = 0.038), AZ (-4.54; p = 0.032), and placebo (-3.03; p < 0.001), improving the rTNSS by 39% beyond the contribution of FP. All individual nasal symptoms contributed to the efficacy of MP29-02. Onset of action was within 30 minutes. MP29-02 significantly improved rTOSS compared with placebo, provided a clinically important improvement in the overall RQLQ score, and was well tolerated. In this study, MP29-02 provided more complete symptom relief than two widely used first-line AR treatments and was well tolerated.