This meta-analysis aimed to assess the effectiveness and safety of (adeno)tonsillectomy (AT) for uncomplicated pediatric obstructive sleep apnea (OSA) across different age groups. Four electronic databases were searched until April 2022, and 93 studies (9087 participants) were selected, including before-after studies, cohort studies, and randomized controlled trials. It has been suggested that age, disease severity, and length of follow-up are associated with surgical effects. Compared with older children (>7 years), patients receiving AT surgery before the age of 7 exhibited a significantly greater release of disease severity, as well as a greater decrease in hypoxemic burden, improvement in sleep quality, and better cardiovascular function. Cognitive/behavioral performance also improved after AT, although it was more related to the length of follow-up than the age at surgery. Notably, the surgical complication rate was considerably higher in patients younger than 3 years old. Overall, we suggest that the age of 3–7 years might be optimal for AT in polysomnography-diagnosed uncomplicated OSA to maximize potential benefits for both disease and comorbidities and balance the risks of surgery.