Adenotonsillar problems might affect the voices of patients with pediatric dysphonia, which is very common. This study aimed to evaluate the prevalence of dysphonia in patients with adenotonsillar problems and to demonstrate the impact of tonsillectomy and adenoidectomy (T & A) on their voice postoperatively. Single-institution retrospective study. Subjects were recruited from those children admitted for the purpose of T & A, and all underwent the auditory-perceptual assessment by speech therapists preoperatively. If children demonstrated scores >2 in the G parameter, we performed subjective (pediatric voice handicap index [pVHI], severity, talkativeness scale) and objective (Multi-Dimensional Voice Program) voice analyses preoperatively and 1 and 3 months postoperatively. Among the 1,197 patients, 91 (7.6%) patients showed dysphonia with a score >2 in the G parameter preoperatively. The follow-up voice analysis was completed in 51 and 22 patients after 1 and 3 months, respectively. Although there were no significant differences in the amount of speech preoperatively and postoperatively, the average visual analog scale score for dysphonia severity was significantly decreased at postoperative 1 month and postoperative 3 months. The average total pVHI score, jitter, shimmer, noise-to-harmonic ratio, and soft phonation index were significantly decreased at 1 and 3 months postoperatively. Subjective scores given by parents did not correlate with the acoustic parameters; however, the postoperative subjective parameters were significantly correlated with objective parameters. Voice problems were significantly improved after T & A in the short term and long term. In those with pediatric dysphonia, decreased mouth breathing and compliance with vocal hygiene would be helpful for voice improvement. 4 Laryngoscope, 131:2369-2375, 2021. © 2021 The American Laryngological, Rhinological and Otological Society, Inc.