Background: Despite perceiving their child as being above a healthy weight, many parents do not intervene. Little is known about the factors influencing parental action. We assessed parental perception of child's weight status, the prevalence of mitigating parental action, and the underlying factors. Methods: We studied 20,242 children and adolescents from 6 centers across China. Anthropometry was measured by research nurses. Parents answered questionnaires, including their perception of their child's weight status, and any subsequent weight treatment. Results: A total of 3254 children had obesity (16.1%), with 63.0% correctly perceived as overweight by their parents. These children were more likely to be older (>= 8 years; p < 0.0001), have severe obesity [adjusted relative risk (aRR) 1.41; p < 0.0001], and have mothers with overweight/obesity (aRR 1.15; p < 0.0001). In particular, parents of children aged <8 years were over five times more likely to perceive their child with overweight/obesity as "thin" than parents of teenagers. Conversely, girls, older children/adolescents, and urban youth were more likely to be wrongly perceived by parents as having an overweight issue. Only one in four children (27.8%) with available information received treatment for their perceived weight problem. Children with severe obesity were more likely to be treated (aRR 1.34; p < 0.0001), as were children of mothers with overweight/obesity (aRR 1.18; p = 0.002). Conclusions: Only one in four Chinese children perceived as overweight by their parents received treatment for their weight problem. Given that overweight/obesity in childhood tracks into adulthood and many parents did not intervene despite perceiving an overweight problem in their child, interventions for childhood obesity need to extend beyond parental perception of children's weight status.