Objective To evaluate the sleep quality of children diagnosed with allergic rhinitis before and after treatment, and to investigate the relationship between allergic rhinitis treatment and sleep quality. Patients and methods This cross-sectional study included 167 patients aged 8–18 years, diagnosed with allergic rhinitis at the Pediatric Allergy and Immunology Outpatient Clinic of the University of Health Sciences Ümraniye Training and Research Hospital between March and July 2023. Patients with comorbid conditions or a pre-existing diagnosis of sleep disorder were excluded. Sleep quality was assessed using the Pittsburgh Sleep Quality Index before the initiation of treatment and again one month later. Symptom severity was measured using the Total Nasal Symptom Score. Results Of the 167 participants, 84 (50.3%) were female; the median age was 11 years. Sensitization to at least one allergen was detected in 129 patients (77.2%). After treatment, total nasal symptom scores decreased significantly compared with baseline (P < 0.001). A strong and statistically significant reduction was observed in total Pittsburgh Sleep Quality Index scores, together with a marked improvement in sleep quality (P < 0.001). Before treatment, 139 patients (83.2%) had poor sleep quality, decreasing to 9 patients (5.4%) after treatment. A significant correlation was identified between the reduction in symptom severity and the improvement in sleep quality (P < 0.001). Conclusion Appropriate treatment improves sleep quality in children with allergic rhinitis. Clinicians should therefore routinely assess sleep quality in pediatric patients with allergic rhinitis, both before and after treatment.