This study aimed to refine and validate a multidomain developmental survey (MDS) used by the Brain Balance® (BB) program. Data were analyzed on 47,571 participants (68.5% male; 4–18 years) whose parents completed the survey before/after 3 months of in-center BB participation. Exploratory Factor Analysis was applied to a training sample (n = 28,254), reducing the original item pool from 98 to 31 items and suggesting a six-factor solution. The six factors were labeled as negative emotionality, reading/writing difficulties, hyperactive-disruptive, academic disengagement, motor/coordination problems, and social communication problems. Exploratory Structural Equation Modeling was applied to two validation samples (n = 9394 and 9923), and the factor structure demonstrated strong goodness-of-fit. Test–retest reliability coefficients (per Pearson correlations) were high for each of the subscales. Finally, the survey’s factor structure appeared equivalent across four groups stratified by reported gender and adolescent status. Overall, the BB-MDS demonstrated strong measurement properties, including validated factor structure, internal reliability, test–retest reliability, and measurement invariance.