Intranasal corticosteroids are considered the most effective therapy for moderate-to-severe seasonal allergic rhinitis (SAR) and recommended first line in guidelines. It is uncertain whether intranasal antihistamines have comparable efficacy. This study was designed to compare the efficacy of azelastine (AZE; 137 μg/spray) and fluticasone propionate (FP; 50 μg/spray), both given as 1 spray/nostril bid (i.e., approved dosing regimen in the United States), in SAR via a post hoc analysis of data from a previously published direct-comparison study. Six hundred ten moderate-to-severe SAR patients (≥12 years old) were randomized into a double-blind, placebo-controlled, parallel-group trial. The primary efficacy variable was change from baseline in reflective total nasal symptom score (rTNSS (morning and evening), over 14 days. Reflective total ocular symptom score (rTOSS) was a key secondary variable. Reflective total of seven symptom scores (rT7SS [nasal plus ocular symptoms]) and time to ≥50% reduction from baseline in these key parameters were also analyzed. AZE and FP reduced rTNSS from baseline by a similar degree (-3.25 versus -3.84; p = 0.2014). Patients experienced comparable improvement in rTOSS (-2.62 versus -2.17; p = 0.2371) and rT7SS (-5.83 versus -6.05; p = 0.7820). FP was superior to AZE in alleviating rhinorrhea (-1.15 versus -0.87; p = 0.0433), but AZE showed comparable efficacy for all other nasal and ocular symptoms. There was no clinically or statistically significant difference between AZE (-1.17) and FP (-1.43) for reduction in the overall rhinitis quality of life questionnaire score (although FP, but not AZE, significantly differed from placebo). A similar proportion of patients in the AZE and FP groups achieved a 50% reduction in rTNSS. However, more AZE patients (53.0%) exhibited a 50% reduction in rTOSS by day 14 versus FP (39.6%), and ≤3 days faster (p = 0.028). Intranasal AZE (137 micrograms/spray) and intranasal FP (50 micrograms/spray), both 1 spray/nostril b.i.d., had comparable efficacy in symptom control in moderate-to-severe SAR.