ObjectiveThe primary objective of this study was to develop and validate a Social Cognitive Theory-based instrument to identify psychosocial factors that influence diet and physical activity among Chinese children aged 10–12 years. DesignThis is a cross-sectional study, with data collected from questionnaires. SettingTwo elementary schools in Beijing, China. ParticipantsFourth to sixth-grade students (N = 1,486) aged 10–12 years were recruited. Variables MeasuredGender, height, weight, nation, and grade were collected. Energy-balanced eating behaviors and their related sociopsychological factors were surveyed. AnalysisConfirmatory factor analysis, Pearson correlations, Cronbach α index, and mediation analysis were used. Results(1) Confirmatory factor analysis revealed a 6-factor solution (51 items) and all factor loadings > 0.32, indicating that the model fitness was acceptable. (2) All correlation coefficients are statistically significant. All of the Cronbach α indexes were > 0.65, indicating acceptable reliability. (3) The mediating effect of goal intention and outcome expectations between self-efficacy and habit strength was statistically significant (P < 0.01), verifying the theory structure. Conclusions and ImplicationsThis questionnaire exhibits good internal consistency, reliability, and structural validity. It can be effectively employed to investigate energy-balanced eating behaviors related to the Social Cognitive Theory in Chinese children.