Abstract Background Perceptions of children's weight status may be important in obesity prevention and treatment. Aims This review identifies the prevalence of the underestimation of overweight status in children by parents/main carers, children, and healthcare professionals (HCP). The review critically synthesized both quantitative and qualitative evidence to explore the factors associated with this underestimation. The diverse methods used to assess this phenomenon are reported. Methods Pooled effect sizes were calculated using random‐effects model. Published studies, up to 2020, were accessed using the following search engines: CINAHL, EMBASE, PUBMED, and Psych‐Info and including the “Cited by” and “Related Articles” functions. Hand‐searching was used to retrieve further articles. Publication language and location had no bearing on the nature of the included studies. Results A total of 91 articles were included. In the quantitative studies, 55% (95% CI 49%–61%) of caregivers underestimated their child's level of overweight and obesity using a verbal scale and 47% (95% CI 36%–55%) using visual scales. Of the children studied, 34% (95% CI 25%–43%) underestimated their own level of overweight and obesity using both scales. In (n = 3) articles, HCPs reflected this misperception, but limited studies prevented meta‐analysis. Underestimation was associated with the child's age, gender, BMI and parental weight status, ethnicity and education. In the qualitative studies, parents/main carers of children with overweight and obesity described their child's weight in terms other than overweight, for example, “big boned,” “thick,” and “solid.” Conclusion The results confirm the prevalence of underestimation of child overweight status across international studies. Understanding the factors which lead to this inaccuracy may help to improve communication within the therapeutic triad and facilitate the recognition and management of children's overweight status.