The multidimensional nature of child well-being requires valid and reliable tools for assessing children's multiple developmental outcomes. This study reports the psychometric properties of the Multidimensional Child Well-Being Scale (MCWBS), a 23-item self-report measure developed on the basis of a sample of school-aged children in China (N = 1322; M = 11.8; SD = 1.56). Exploratory factor analysis identified four well-being factors, namely, Physical, Psychological, Social, and Educational. The four-factor structure is further validated by confirmatory factor analysis (CFA). Cronbach's alpha for the total scale (alpha = 0.894) and each subscale (0.857 for physical well-being; 0.917 for psychological well-being; 0.801 for social well-being; and 0.805 for educational well-being) were satisfactory, indicating high reliability. MCWBS positively correlated with quality of life (r = 0.674,p < 0.01) and happiness (r = 0.519,p < 0.01), and negatively correlated with depressive symptoms (r = -0.437,p < 0.01), indicating convergent validity. Multi-group CFA provided support for gender, hukou, and age-related invariance of the MCWBS at the configural, metric, and scalar level. Overall, this study addresses the measurement gap by developing a reliable and valid instrument containing multiple domains of children's development outcomes, which can contribute to the child well-being research and practice.