Unplanned reoperations have not been studied extensively in pediatric patients, especially concerning risk factors. We aim to estimate the rate of unplanned reoperations and to determine the associated factors in pediatric general surgical specialties.This analysis included a retrospective case-control study of unplanned reoperations from July 1, 2010 to June 30, 2017 in the general surgical specialties. For each case, we identified approximately 2 randomly selected controls who underwent the same type of operation. The factors involved in the unplanned reoperations were investigated using univariate and multivariate analysis.Of the 3263 patients who underwent surgery, unplanned reoperations were performed in 139 patients (4.3%). The main indications for unplanned reoperations were wound complications (n = 52, 42.6%), followed by postoperative ileus (n = 12, 9.8%), postoperative bleeding (n = 8, 6.6%), and intraabdominal infection (n = 13, 10.7%). Following multivariate analysis, 2 factors remained significantly associated with unplanned reoperation: higher initial surgery-related risk level (P = .007, risk ratio (RR) = 0.48; 95% confidence interval (CI) = 0.27-0.82) and operation performed outside working hours (P = .031, RR = 0.52; 95% CI = 0.30-0.89).Various patient- and procedure-related factors were associated with unplanned reoperations. This information might be helpful for the optimization of treatment planning and resource allocation.