We conducted an Umbrella review of eligible studies to evaluate what patient features have been investigated in the multisystem inflammatory syndrome in children (MIS-C) population, in order to guide future investigations. We comprehensively searched MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from December 1, 2019 to the May 6, 2022. The time period was limited to cover the coronavirus disease-2019 (COVID-19) pandemic period. The protocol was registered in the PROSPERO registry (CRD42022340228). Eligible studies included (1) a study population of pediatric patients ≤21 years of age diagnosed with MIS-C; (2) an original Systematic review or Mata-analysis; (3) published 2020 afterward; and (4) was published in English. A total of 41 studies met inclusion criteria and underwent qualitative analysis. 28 studies reported outcome data of MIS-C. 22 studies selected clinical features of MIS-C, and 6 studies chose demographic data as a main topic. The mortality rate for children with MIS-C was 1.9% (interquartile range (IQR) 0.48), the ICU admission rate was 72.6% (IQR 8.3), and the extracorporeal membrane oxygenation rate was 4.7% (IQR 2.0). A meta-analysis of eligible studies found that cerebral natriuretic peptide in children with MIS-C was higher than that in children with COVID-19, and that the use of intravenous immunoglobulin (IVIG) in combination with glucocorticoids to treat MIS-C compared to IVIG alone was associated with lower treatment failure. In the future, for patients with MIS-C, studies focused on safety of surgery requiring general anesthesia, risk factors, treatment, and long-term outcomes are warranted.