Objective: Seasonal allergic rhinitis (SAR) is a common disease of childhood and is characterized by type 2 inflammation, bothersome symptoms, and impaired quality of life (QoL). Intranasal corticosteroids are effective medications in managing SAR. In addition, mometasone furoate nasal spray (MFNS) is a well-known therapeutic option. However, the literature provided no data about the effects of MFNS in European children with SAR. Thus, this study addressed this unmet requirement. Methods: MFNS was compared to isotonic saline. Both treatments were prescribed: one drop of spray per nostril, twice a day, for 3 weeks. Nasal cytology, total symptom score (TSS), visual analogic scale concerning the parental perception of severity of symptoms, and the Pediatric Rhinoconjunctivitis Quality of Life Questionnaire (PRQLQ) were assessed at baseline, after 7 and 21 days, and 1 month after discontinuation. Results: MFNS significantly reduced eosinophil and mast cell counts, improved QoL, and relieved symptoms, as assessed by doctors and perceived by parents. These effects persisted over time, even after discontinuation. Both treatments were safe and well-tolerated. Conclusions: The present study documented that a 3-week MFNS treatment was able to significantly dampen type 2 inflammation, improve QoL, and reduce severity of symptoms in Italian children with SAR, and was safe.