We performed a systematic review and meta-analysis to evaluate the risk of the development of cancers in patients with pediatric-onset inflammatory bowel disease (IBD). A computerized literature search was performed. The primary outcome was the pooled incidence of cancer in studies reporting the risk as a standardized incidence ratio (SIR). The secondary outcomes were the pooled incidence rates of all cancers and site-specific cancers including colorectal cancer (CRC) and hematologic cancers. 66 studies reporting outcomes in 38,092 patients were included. The pooled SIR for cancer was 2.39 (P < .0001, 95% confidence interval (CI) = 2.00-2.86) in IBD. The pooled incidence rates for cancer in Crohn's disease (CD) and ulcerative colitis (UC) patients were 0.014 (95% CI = 0.0087-0.021) and 0.031 (95% CI = 0.018-0.052), respectively. The pooled incidence rate of CRC in CD and UC were 0.0075 (95% CI = 0.0049-0.011) and 0.020 (95% CI = 0.012-0.034), respectively. The pooled rates of hematologic cancers in CD and UC were 0.0061 (95% CI = 0.0040-0.0090) and 0.0045 (95% CI = 0.0026-0.0079), respectively. Cumulative meta-analyses showed a decreasing trend in the incidence of these cancers in both CD and UC. Patients with pediatric-onset IBD had an increased risk of cancers development compared with the general population, however, incidence appeared to be decreasing in recent years. Copyright © 2020 Elsevier Inc. All rights reserved.