Objectives: The tonsillar retractor used during adenotonsillectomy, one of the most common pediatric surgeries, may increase sympathetic activity. This study aimed to evaluate the effect of tonsillar retractor insertion on intracranial pressure (ICP) and intraocular pressure (IOP) in children undergoing adenotonsillectomy. Methods: This prospective observational study included 24 pediatric patients undergoing adenotonsillectomy and 20 age-matched controls undergoing other surgeries. Bilateral optic nerve sheath diameters (ONSD) were measured by ultrasonography, and IOP was assessed by tonometry before and immediately after tonsillar retractor insertion. Hemodynamic parameters were also recorded at the same time points and compared between groups. Pressure changes were analyzed using the Generalized Estimating Equation method, and effect sizes were calculated with Cohen's d. Results: Insertion of the tonsillar retractor caused a significant increase in mean ONSD from 4.66 ± 0.58 mm to 5.61 ± 0.52 mm (p < 0.001, d = 2.36). Mean IOP rose significantly from 13.7 ± 2.8 mmHg to 18.2 ± 5.3 mmHg (p < 0.001, d = 0.97). Systolic blood pressure increased from 100.4 ± 10.1 mmHg to 108.5 ± 10.8 mmHg (p = 0.0008), whereas diastolic pressure changes were not significant (p = 0.097). No significant correlation was found between changes in ONSD and IOP (r = −0.22, p = 0.30). Conclusion: Tonsillar retractor use during adenotonsillectomy results in a rapid, marked rise in ICP and IOP. These findings should be considered by otolaryngologists and anesthesiologists managing pediatric patients at risk of sympathetic surges. Level of Evidence: 2.