ObjectiveTo examine the phenomenon of pain catastrophizing among the principal caregivers of postoperative children with malignant bone tumors and explore its impact on pain perception and kinesiophobia in children. DesignA cross-sectional study design. MethodsUsing a cross-sectional study design, a questionnaire-based survey was conducted among 140 children with malignant bone tumors and their principal caregivers, who were admitted to a tertiary hospital in Shanghai from 2020 to 2023. Pearson's univariate and multiple regression analyses were conducted. The questionnaire included general data, the Parental Pain Catastrophizing Scale, the Short-Form McGill Pain Questionnaire, and the Tampa Scale of Kinesiophobia. ResultsThe frequency of pain catastrophizing for the principal caregivers was 16.8%. The frequency of kinesiophobia in children was 93.1%. The level of pain catastrophizing was positively correlated with the level of kinesiophobia and pain perception (r = 0.556, 0.614, p < 0.05). Multiple logistic regression analysis showed that the level of pain catastrophizing in principal caregivers was an important factor of kinesiophobia in children (B = 0.370, Std. = 0.119, Wald = 9.687, Ex (P) = 1.448, p = 0.002). Multiple linear regression analysis showed that the incidence of pain catastrophizing and the level of kinesiophobia were important influencing factors in pain perception (p < 0.05), with R2 = 0.272, adjusted R2 = 0.249, F = 11.579, and p < 0.001. ConclusionsThe level of pain catastrophizing in the principal caregivers was an important factor in postoperative kinesiophobia and pain perception in children with a malignant bone tumor. Practice implicationsIt is important to evaluate the patients' and their families' emotional changes and psychological needs during the perioperative period. Nurses play a crucial role in providing appropriate interventions for patients or families to reduce the negative pain experience and improve patients’ prognosis.