Objective: Construct validity for the Motor Development Scale (MDS) has not been established. The aim of this study was to examine whether the unidimensional model of MDS would be appropriate for children aged 4 to 6 years-old and provide construct validity for the items concerning this age group in Brazil. Methods: A total of 938 children participated in the study (214 4-year-olds, 643 5-year-olds, and 81 6-year-olds). Confirmatory factor analysis (CFA) was used to evaluate construct validity of the MDS using a unidimensional model. Results: The CFA for the unidimensional model showed excellent adequacy indices for age 4: χ2 (2) = 0.581, p = 0.748, comparative fit index (CFI) = 1.000, Tucker-Lewis index (TLI) = 1.090, root mean square error of approximation (RMSEA) = 0.000 (90% confidence interval [90%CI] = 0.000 to 0.093, close fit [Cfit] = 0.841); age 5: χ2 (2) = 2.669, p = 0.263, CFI = 0.993, TLI = 0.980, RMSEA = 0.023 (90%CI = 0.000 to 0.085, Cfit = 0.682), weighted root mean square residual (WRMR) = 0.407; and age 6: χ2 (9) = 8.275, p = 0.506, CFI = 1.000, TLI = 1.010, RMSEA = 0.000 (90%CI = 0.000 to 0.118, Cfit = 0.653), WRMR = 0.495. Reliability was good: ω = 0.87 (95%CI = 0.81 to 0.92). Conclusion: The proposed unidimensional solution for the MDS provides a concise, parsimonious and reliable way to assess motor development in children aged 4 to 6 years.