Purpose Traditional and complementary medicine (T&CM) strategies are commonly used in pediatric oncology. Patterns may vary based on country income. We systematically reviewed published studies describing T&CM use among pediatric oncology patients in low-income countries (LIC/LMIC), middle-income countries (UMIC), and high-income countries (HIC). Objectives included describing estimated prevalence of use, reasons for use, perceived effectiveness, modalities used, rates of disclosure, and reporting of delayed or abandoned treatment. Methods MEDLINE, EMBASE, Global Health, CINAHL, PsycINFO, Allied and Complementary Medicine Database, Cochrane Database of Systematic Reviews, and ProceedingsFirst were searched. Inclusion criteria were primary studies involving children younger than the age of 18 years, undergoing active treatment of cancer, and any T&CM use. Exclusion criteria included no pediatric oncology–specific outcomes and studies involving only children off active treatment. Data were extracted by two reviewers using a systematic data extraction form determined a priori. Results Sixty-five studies published between 1977 and 2015 were included, representing 61 unique data sets and 7,219 children from 34 countries. The prevalence of T&CM use ranged from 6% to 100%. Median rates of use were significantly different in LIC/LMIC (66.7% ± 19%), UMIC (60% ± 26%), and HIC (47.2% ± 20%; P = .02). Rates of disclosure differed significantly by country income, with higher median rates in HIC. Seven studies reported on treatment abandonment or delays. Conclusion The use of T&CM in pediatric oncology is common worldwide, with higher median prevalence of use reported in LIC/LMIC. Further research is warranted to examine the impact on treatment abandonment and delay.